Image displaying apparatus and optical Apparatus

ABSTRACT

The image displaying apparatus includes an image production apparatus, a first light conduction section and a second light conduction section. The first light conduction section includes a first light conduction plate which propagates part of incident light thereto by total reflection in the inside thereof and emits the propagated light, and a reflection type volume hologram diffraction grating disposed on the first light conduction plate. The second light conduction section includes a second light conduction plate, a first deflection section and a second deflection section.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an optical apparatus and an image displayingapparatus in which the optical apparatus is incorporated.

2. Description of the Related Art

A virtual image displaying apparatus as an image displaying apparatuswherein a virtual image optical system allows a two-dimensional imageformed by an image formation apparatus to be observed as an enlargedvirtual image by an observer is well known, for example, fromJP-T-2005-521099 and Japanese Patent Laid-Open No. 2006-162767.

As conceptually illustrated in FIG. 25, the image displaying apparatus900 mentioned includes an image formation apparatus 911 including aplurality of pixels arranged in a two-dimensional matrix, a collimateoptical system 912 for converting light emitted from the pixels of theimage formation apparatus 911 into parallel light and a light conductionsection 930 for receiving, conducting and emitting the parallel lightfrom the collimate optical system 912. The light conduction section 930includes a light conduction plate 931 for propagating incident light inthe inside thereof by total reflection and then emitting the propagatedlight therefrom, a first deflection section 940 formed, for example,from a single-layer light reflecting film for reflecting the lightincident to the light conduction plate 931 such that the light incidentto the light conduction plate 931 is totally reflected in the inside ofthe light conduction plate 931 and a second deflection section 950formed, for example, from a light reflecting multi-layer film having amulti-layer lamination structure for emitting the light propagated inthe inside of the light conduction plate 931 by total reflection fromthe light conduction plate 931. If, for example, a head-mounted display(HMD) unit is formed from such an image displaying apparatus 900 asdescribed above, then reduction in weight and size of the apparatus canbe achieved.

Alternatively, a virtual image displaying apparatus as an imagedisplaying apparatus in which a hologram diffraction grating is used inorder to allow an observer to observe a two-dimensional image formed byan image formation apparatus as an enlarged virtual image by a virtualimage optical system is known, for example, from Japanese PatentLaid-Open No. 2007-094175 and Japanese Patent Laid-Open No. 2007-012530.

As conceptually illustrated in FIGS. 26 and 27, the image displayingapparatus 1000 mentioned above includes, as basic components thereof, animage formation apparatus 1011 for displaying an image, a collimateoptical system 1012 and a virtual image optical system or lightconduction section 1030 which receives light displayed by the imageformation apparatus 1011 and conducts the inputted light to the pupil 41of an observer. The light conduction section 1030 includes a lightconduction plate 1031, and a first diffraction grating member 1040 and asecond diffraction grating member 1050 provided on the light conductionplate 1031 and individually formed from a reflection type volumehologram diffraction grating. Light emitted from pixels of the imageformation apparatus 1011 is inputted to the collimate optical system1012, and parallel light is produced by the collimate optical system1012 and then is introduced to the light conduction plate 1031. Theparallel light enters and outgoes from a first face 1032 of the lightconduction plate 1031. Meanwhile, the first diffraction grating member1040 and the second diffraction grating member 1050 are mounted on asecond face 1033 of the light conduction plate 1031 which extends inparallel to the first face 1032 of the light conduction plate 1031.

SUMMARY OF THE INVENTION

On an XY plane shown in FIG. 26, image displaying light emitted from theimage formation apparatus 1011 is converted into a parallel light fluxgroup wherein the angles of view, that is, the outgoing angles of lightemitted from the pixels of the image formation apparatus 1011, aredifferent from each other by the collimate optical system 1012. Theparallel light flux group is converted into a light flux group whereinthe angles of view are different from each other on an XZ planeorthogonal to the XY plane and is introduced to the light conductionplate 1031. It is to be noted that, in FIG. 26, representative parallellight fluxes on the XY plane are indicated by parallel light fluxes r₁represented by a solid line, r₂ represented by an alternate long andshort dash line and r₃ represented by a broken line. Further, in FIG.27, representative parallel fluxes on the XZ plane are indicated byparallel light fluxes R₁ represented by a solid line, R₂ represented byan alternate long and short dash line and R₃ represented by a brokenline.

In the image displaying apparatus 1000 shown in FIGS. 26 and 27, aleftward and rightward, that is, horizontal, direction and an upward anddownward, that is, vertical, direction are defined as a Y direction anda Z direction, respectively. In particular, image displaying light fordisplaying an image, various kinds of information and so forth isconducted from a transverse direction to the pupil 41 of an observer andenters the pupil 41. It is to be noted that, where the image displayingapparatus 1000 is applied to a head-mounted type display (HMD) unit, theimage formation apparatus and so forth are disposed not above the pupil41 but in a transverse direction with respect to the pupil 41 so thatgood observation of the external world can be implemented.

On the other hand, with such a configuration as described above, sincethe propagation distance of the light conducted in the inside of thelight conduction plate 1031 becomes comparatively long, a problem givenbelow appears.

Here, in the configuration described above, the image displaying lightinputted from the first face 1032 of the light conduction plate 1031 isinputted to the first diffraction grating member 1040 formed from areflection type volume hologram diffraction grating disposed on thesecond face 1033 which is a position opposing to the first face 1032. Itis to be noted that the reflection type volume hologram diffractiongrating has a configuration having a uniform interference fringe pitchon the hologram surface irrespective of a position.

Regarding an X direction component on the XY plane, the light fluxes r₁,r₂ and r₃ of the light diffraction reflected by the first diffractiongrating member 1040 in the light conduction plate 1031 are conducted asparallel light fluxes while repetitively totally reflecting between thefirst face 1032 and the second face 1033, and advances in a Y directiontoward the second diffraction grating member 1050 formed from areflection type volume hologram diffraction grating and provided on theother end of the light conduction plate 1031. Here, since the lightconduction plate 1031 is thin and a path of the light which advances inthe light conduction plate 1031 is comparatively long as describedabove, the number of times of total reflection to the second diffractiongrating member 1050 is different depending upon a horizontal angle ofview as shown in FIG. 26. Therefore, the number of times of reflectionof the parallel light r₃ inputted while inclining to the seconddiffraction grating member 1050 (that is, whose horizontal angle of viewis positive) from among the parallel light r₁, r₂ and r₃ inputted to thelight conduction plate 1031 is smaller than the number of times ofreflection of the parallel light r₁ inputted to the light conductionplate 1031 with an angle in the opposite direction to the direction ofthe parallel light r₃ (that is, whose horizontal angle of view isnegative). In particular, since the interference fringe pitch on thehologram surface of the first diffraction grating member 1040 isuniform, regarding the outgoing angle of diffraction reflection in thefirst diffraction grating member 1040, the parallel light r₃ whosehorizontal angle of view is positive is greater than the parallel lightr₁ whose horizontal angle of view is negative. Then, the parallel lightof angles of view inputted to the second diffraction grating member 1050goes beside from the total reflection condition by the diffractionreflection, and is emitted from the light, conduction plate 1031 andthen inputted to the pupil 41 of the observer.

In this manner, in the advancing direction of the parallel light fluxes,the number of times of reflection in the light conduction plate 1031 isdifferent depending upon the horizontal angle of view. In other words,the optical path length is different. However, since all of thepropagated light fluxes are parallel light fluxes, as it were, a lightflux group advances in such a manner as to be folded. As it is apparentif inverse ray tracing is carried out in the configuration shown in FIG.14 of Japanese Patent Laid-Open No. 2007-12530, there exists a lightflux which is returned and reflected at a position extending over theedge portion of the first diffraction grating member 1040 and the secondface 1033 from within the light flux group. If the inverse ray tracingis carried out, then part of the light fluxes (that is, a portionreflected on the second face 1033) is repetitively reflected to bediffracted at a different position of the first diffraction gratingmember 1040 to reach the collimate optical system 1012. On the otherhand, the remaining light fluxes are diffracted at an end portion of thefirst diffraction grating member 1040 to reach the collimate opticalsystem 1012 as they are. In particular, while the light fluxes areparallel light fluxes emitted from the same pixel and having the sameangles of view, there exists a light flux which is diffraction reflectedat a different portion of the first diffraction grating member 1040 tobe multiplexed in the light conduction plate 1031 to propagate.

In this manner, the width regarding the Y direction of a necessary lightflux in such an optical system as described above, that is, an aperturestop width in the Y direction, is determined by an end point at whichthe light flux is folded. On the light conduction plate 1031, theposition of the first diffraction grating member 1040 on which theparallel light flux group emitted from the collimate optical system 1012and inputted to the light conduction plate 1031 is diffraction reflectedis determined as the aperture stop position in the Y direction.

On the other hand, regarding the incoming light R₁, R₂ and R₃ whosehorizontal angles of view are different from each other on the XZ plane,while the X direction component is repetitively reflected in the lightconduction plate 1031, the Z direction component reaches an emergingportion without being reflected. In particular, the light emitted fromthe collimate optical system 1012 is converged and inputted from thefirst face 1032 on the XZ plane and then advances in the Y direction inthe light conduction plate 1031. Then, the light fluxes advance whilebeing reflected on the first face 1032 and the second face 1033 of thelight conduction plate 1031 so as to spread in the Z direction untilthey come to the second diffraction grating member 1050. Then, the lightfluxes are reflected and diffracted by and then emitted from thediffraction grating member 1050 so that they are introduced to the pupil41 of the observer. In this manner, in the image displaying apparatus1000, the necessary width of the light fluxes in the Z direction, thatis, the aperture stop width in the Z direction, is determined dependingupon the position of the pupil 41 of the observer.

Since the aperture stop position in the Z direction is the position ofthe pupil 41 of the observer, the distance from the collimate opticalsystem 1012 to the aperture stop position in the Z direction is equal tothe sum of the distance over which the light is repetitively totallyreflected and propagated in the inside of the light conduction plate1031 and the distance from the light conduction plate 1031 to the pupil41 of the observer. Therefore, the distance is very long. On the otherhand, since the aperture stop position in the Y direction is theposition of the first diffraction grating member 1040 disposed on thelight conduction plate 1031, the distance to the aperture stop positionin the Y direction can be made smaller than that to the aperture stopposition in the Z direction. In this manner, since the distance to theaperture stop position is great in the Z direction, the diameter of thecollimate optical system 1012 in the Z direction must be set greaterthan the diameter in the Y direction.

Further, where the diameter of the aperture stop in the Z direction inthe image formation apparatus 911 and 1011 is set great, the light rayangle of the peripheral angle of view becomes great in an image emittedfrom the image formation apparatus 911 and 1011. As a result, thedisplay contrast in a liquid crystal display apparatus or the like usedin the image formation apparatus 911 and 1011 decreases and makes acause of degradation of the picture quality.

Accordingly, it is desirable to provide an image displaying apparatuswhich allows an observer to observe a two-dimensional image formed by animage formation apparatus as an enlarged virtual image by means of avirtual image optical system and wherein there is no necessity to use alens of a large diameter in the image formation apparatus and an opticalapparatus suitable to incorporate in the image displaying apparatus.

According to a first mode of the present invention, there is provided animage displaying apparatus including:

(A) an image production apparatus;

(B) a first light conduction section adapted to receive, conduct andemit a light emitted from the image production apparatus; and

(C) a second light conduction section adapted to receive and conductlight emitted from the first light conduction section and then emit thelight toward the pupil of an observer,

the first light conduction section including

-   -   (B-1) a first light conduction plate for propagating part of the        incident light by total reflection in the inside thereof and        emitting the light therefrom, and    -   (B-2) a reflection type volume hologram diffraction grating        disposed on the first light conduction plate,

the second light conduction section including

-   -   (C-1) a second light conduction plate adapted to propagate        incoming light in the inside thereof by total reflection and        then emit the light,    -   (C-2) a first deflection section disposed in the second light        conduction plate and adapted to deflect light incident to the        second light conduction plate such that the light introduced to        the second light conduction plate is totally reflected in the        inside of the second light conduction plate, and    -   (C-3) a second deflection section disposed in the second light        conduction plate and adapted to deflect the light propagated in        the inside of the second light conduction plate by total        reflection over a plural number of times in order to emit the        light propagated in the inside of the second light conduction        plate by total reflection from the second light conduction        plate.

It is to be noted that the term “total reflection” is used here andhereafter to signify internal total reflection or total reflection inthe inside of the first light conduction plate or of the second lightconduction plate.

According to the first mode of the present invention, there is providedan optical apparatus including:

a first light conduction section configured to receive, conduct and emita light flux; and

a second light conduction section configured to receive and conduct thelight flux emitted from the first light conduction section and then emitthe light toward the pupil of an observer,

the first light conduction section including

-   -   (a-1) a first light conduction plate for propagating part of the        incident light by total reflection in the inside thereof and        emitting the light therefrom, and    -   (a-2) a reflection type volume hologram diffraction grating        disposed on the first light conduction plate,

the second light conduction section including

-   -   (b-1) a second light conduction plate adapted to propagate        incoming light in the inside thereof by total reflection and        then emit the light,    -   (b-2) first deflection section disposed in the second light        conduction plate for deflecting light incident to the second        light conduction plate such that the light introduced to the        second light conduction plate is totally reflected in the inside        of the second light conduction plate, and    -   (b-3) second deflection section disposed in the second light        conduction plate for deflecting the light propagated in the        inside of the second light conduction plate by total reflection        over a plural number of times in order to emit the light        propagated in the inside of the second light conduction plate by        total reflection from the second light conduction plate.

According to a second mode of the present invention, there is providedan image displaying apparatus including:

(A) an image production apparatus; and

(B) a light conduction section configured to receive and conduct lightoutputted from the image production apparatus and then emit the lighttoward the pupil of an observer,

the light conduction section including

-   -   (B-1) a light conduction plate for propagating the incident        light by total reflection in the inside thereof and emitting the        light therefrom,    -   (B-2) a first deflection section disposed in the light        conduction plate and adapted to deflect the light incident to        the light conduction plate so that the light incident to the        light conduction plate is totally reflected in the inside of the        light conduction plate, and    -   (B-3) a second deflection section disposed in the light        conduction plate and configured to deflect the light propagated        in the inside of the light conduction plate by total reflection        over a plural number of times in order to emit the light        propagated in the inside of the light conduction plate by total        reflection from the light conduction plate,

the image displaying apparatus further including

a beam expansion section configured to expand, where an enteringdirection of the light into the light conduction plate and a propagationdirection of the light in the light conduction plate are defined as an Xdirection and a Y direction, respectively, the light emitted from theimage production apparatus along a Z direction and emit the expandedlight to the light conduction section.

According to the second mode of the present invention, there is providedan optical apparatus including:

a light conduction section configured to receive, conduct and emit alight flux,

-   -   the light conduction section including a light conduction plate        for propagating the incident light by total reflection in the        inside thereof and emitting the propagated light therefrom,    -   a first deflection section disposed in the light conduction        plate for deflecting the light incident to the light conduction        plate so that the light incident to the light conduction plate        is totally reflected in the inside of the light conduction        plate, and    -   a second deflection section disposed in the light conduction        plate for deflecting the light propagated in the inside of the        light conduction plate by total reflection over a plural number        of times in order to emit the light propagated in the inside of        the light conduction plate by total reflection from the light        conduction plate,

the optical apparatus further including

beam expansion section configured to expand, where an entering directionof the light flux into the light conduction plate and a propagationdirection of the light in the light conduction plate are defined as an Xdirection and a Y direction, respectively, the light flux along a Zdirection and emit the expanded light to the light conduction means.

According to another mode of the present invention, there is provided animage displaying apparatus, including:

(A) an image production apparatus;

(B) a first light conduction section configured to receive, conduct andemit a light emitted from the image production apparatus; and

(C) a second light conduction section configured to receive and conductlight emitted from the first light conduction section and then emit thelight toward the pupil of an observer,

the first light conduction section including

-   -   (B-1) a first light conduction plate for propagating part of the        incident light by total reflection in the inside thereof and        emitting the light therefrom, and    -   (B-2) a reflection type volume hologram diffraction grating        disposed on the first light conduction plate,

the second light conduction section including

-   -   (C-1) a second light conduction plate configured to propagate        incoming light in the inside thereof by total reflection and        then emit the light;    -   (C-2) a first deflection section disposed in the second light        conduction plate and configured to deflect light incident to the        second light conduction plate, and    -   (C-3) a second deflection section disposed in the second light        conduction plate and configured to deflect the light propagated        in the inside of the second light conduction plate by total        reflection.

According to a further mode of the present invention, there is providedan image displaying apparatus, including:

(A) an image production apparatus; and

(B) a light conduction section configured to receive and conduct lightoutputted from the image production apparatus and then emit the lighttoward the pupil of an observer,

the light conduction section including

-   -   (B-1) a light conduction plate for propagating the incident        light by total reflection in the inside thereof and emitting the        light therefrom,    -   (B-2) a first deflection section disposed in the light        conduction plate and configured to deflect light incident to the        light conduction plate, and    -   (B-3) a second deflection section disposed in the light        conduction plate and configured to deflect the light propagated        in the inside of the light conduction plate by total reflection        over a plural number of times,

the image displaying apparatus further including

a beam expansion section configured to expand, where an enteringdirection of the light into the light conduction plate and a propagationdirection of the light in the light conduction plate are defined as afirst direction and a second direction, respectively, the light emittedfrom the image production apparatus along a third direction differentfrom the first direction and the second direction and emit the expandedlight to the light conduction section.

It is to be noted that the “second light conduction section” in theimage displaying apparatus and the optical apparatus according to thefirst mode of the present invention and the “light conduction section”in the image displaying apparatus and the optical apparatus according tothe second mode of the present invention are substantially same as eachother. Thus, in the description given hereinbelow, the “light conductionsection” in the image display apparatus and the optical apparatusaccording to the second mode of the present invention is referred to as“second light conduction section” for the convenience of description.Similarly, the “second light conduction plate” in the image displayingapparatus and the optical apparatus according to the first mode of thepresent invention and the “light conduction plate” in the imagedisplaying apparatus and the optical apparatus according to the secondmode of the present invention are substantially same as each other.Thus, in the description given hereinbelow, the “light conduction plate”in the image display apparatus and the optical apparatus according tothe second mode of the present invention is referred to as “second lightconduction plate” for the convenience of description.

In the image displaying apparatus and the optical apparatus according tothe first mode of the present invention, the first light conductionsection is disposed between the image production apparatus and thesecond light conduction section and is configured from the first lightconduction plate and the reflection type volume hologram diffractiongrating. Accordingly, the first light conduction section functions as akind of beam expander, that is, as a kind of beam expansion means, andthe shape of a light flux emitted from the image production apparatusand introduced into the first light conduction section is expanded alongthe light propagation direction by the internal total reflection in thefirst light conduction plate by the reflection type volume hologramdiffraction grating. Then, the light flux of the expanded form isintroduced into the second light conduction section. On the other hand,the image displaying apparatus and the optical apparatus according tothe second mode of the present invention include the beam expansionsection for expanding light or a light flux in the Z direction andintroducing the expanded light or light flux to the light conductionsection. Therefore, the necessity for setting the diameter of theaperture stop in the Z direction of the image production apparatus to alarge diameter is eliminated, and the necessity to use a lens of a largediameter in the image production apparatus is eliminated. Consequently,reduction in size and weight of the image displaying apparatus can beanticipated, and such a situation that the display contrast drops andthe picture quality is deteriorated is prevented. Further, while thefirst light conduction section is formed from the reflection type volumehologram diffraction grating, since interference fringes formed on thereflection type volume hologram diffraction grating have a uniform angleand exhibit uniform refractive index modulation over the entiretythereof, there is no necessity for alignment which is difficult and adispersion is less likely to occur.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings inwhich like parts or elements denoted by like reference symbols.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view conceptually showing an image displayingapparatus of an embodiment 1;

FIG. 2 is a similarly view but conceptually showing an image displayingapparatus of an embodiment 2;

FIG. 3A is a view conceptually showing an image displaying apparatus ofan embodiment 3, and FIG. 3B is an enlarged schematic sectional viewshowing part of a reflection type volume hologram diffraction grating ofthe image displaying apparatus of FIG. 3A;

FIG. 4 is a schematic view conceptually showing an image displayingapparatus of an embodiment 4;

FIG. 5A is a view schematically showing an arrangement state of an imageproduction apparatus, a first light conduction section and a secondlight conduction section, and FIG. 5B is a schematic view conceptuallyshowing the first light conduction section in section;

FIG. 6 is a schematic view of a head-mounted type display unit of anembodiment 5 as viewed from the front;

FIG. 7 is a schematic view of the head-mounted type display unit of FIG.6 as viewed from the front with a frame removed;

FIG. 8 is a schematic view of the head-mounted type display unit of FIG.6 as viewed from above;

FIG. 9 is a schematic view, as viewed from above, of the head-mountedtype display unit of FIG. 6 mounted on the head of an observer showingonly the image displaying apparatus with the frame omitted;

FIG. 10 is a schematic view of a head-mounted type display unit of anembodiment 6 as viewed from the front;

FIG. 11 is a schematic view of the head-mounted type display unit ofFIG. 10 as viewed from the front with a frame removed;

FIG. 12 is a schematic view of the head-mounted type display unit ofFIG. 10 as viewed from above;

FIGS. 13A and 13B are views schematically showing arrangement states ofan image production apparatus, a beam expansion section and a lightconduction section in an embodiment 7 and an embodiment 8;

FIG. 14 is a schematic view conceptually showing an image displayingapparatus of the embodiment 7;

FIG. 15 is a schematic view conceptually showing a modification to theimage displaying apparatus of FIG. 14;

FIG. 16 is a schematic view conceptually showing an image displayingapparatus of the embodiment 8;

FIGS. 17, 18 and 19 are similar views but showing differentmodifications to the image displaying apparatus of FIG. 16;

FIG. 20 is a view of a modification to an image formation apparatussuitable for use in image displaying apparatus of FIG. 1 or FIG. 3A;

FIGS. 21, 22, 23 and 24 are similar views but showing severalmodifications to the image formation apparatus suitable of FIG. 20;

FIG. 25 is a schematic view conceptually showing a conventional imagedisplaying apparatus;

FIG. 26 is a schematic view conceptually showing another conventionalimage displaying apparatus;

FIG. 27 is a view of the conventional image displaying apparatus of FIG.25 as viewed from a direction different from that in FIG. 26;

FIGS. 28A and 28B are schematic views of an arrangement state of animage production apparatus, a beam expansion section and a lightconduction section in a working example 9 as viewed in a Y direction anda Z direction, respectively;

FIGS. 29A and 29B are schematic partial sectional views of the beamexpansion section in the working example 9 and FIG. 29C is a schematicview illustrating a state in which light is reflected by the beamexpansion section in the working example 9; and

FIGS. 30A and 30B are schematic views illustrating an arrangement stateof the image production apparatus, the beam expansion section and thelight conduction section in the working example 7 as viewed in a Ydirection and a Z direction, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the present invention is described in detail inconnection with several embodiments thereof with reference to theaccompanying drawings. It is to be noted, however, that the presentinvention is not limited to the embodiments and various numerical valuesand materials applied in the embodiments are given for illustrativepurpose only. It is to be noted that the description is given in thefollowing order.

1. General Description of the Image Displaying Apparatus, OpticalApparatus and Head-Mounted Type Display Unit of the Invention

2. Embodiment 1 (image displaying apparatus and optical apparatusaccording to the first mode of the invention)3. Embodiment 2 (modification to the embodiment 1)4. Embodiment 3 (different modification to the embodiment 1)5. Embodiment 4 (modification to the embodiment 3)6. Embodiment 5 (head-mounted type display unit)7. Embodiment 6 (modification to the head-mounted type display unit)8. Embodiment 7 (image displaying apparatus and optical apparatusaccording to the second mode of the invention)9. Embodiment 8 (modification to the embodiment 7)10. Embodiment 9 (modification to the Embodiment 7) and others

General Description of the Image Displaying Apparatus and the OpticalApparatus of the Invention

The image display apparatus according to the first mode or the secondmode of the present invention may be configured such that the imageproduction apparatus includes:

(A-1) an image formation apparatus having a plurality of pixels arrayedin a two-dimensional matrix; and

(A-2) a collimate optical system for converting light emitted from thepixels of the image formation apparatus into parallel light; and

a light flux of the parallel light obtained by the conversion by thecollimate optical system is introduced to the first light conductionsection or the beam expansion section. It is to be noted that the imageproduction apparatus having such a configuration as just described ishereinafter referred to as “image production apparatus of the firstform.”

Alternatively, the image display apparatus according to the first modeor the second mode of the present invention may be configured such thatthe image production apparatus includes:

(A-1) a light source;

(A-2) a collimate optical system for converting light emitted from thelight source into parallel light;

(A-3) a scanning section for scanning the parallel light emitted fromthe collimate optical system; and

(A-4) a relay optical system for relaying the parallel light scanned bythe scanning section; and

a light flux of the parallel light obtained by the conversion by therelay optical system is introduced to the first light conduction sectionor the beam expansion section. It is to be noted that the imageproduction apparatus having such a configuration as just described ishereinafter referred to as “image production apparatus of the secondform.”

The image displaying apparatus according to the first mode of thepresent invention including the image production apparatus of the firstform and the image production apparatus of the second form (such imagedisplaying apparatus may be hereinafter referred to generally as “imagedisplaying apparatus according to the first mode”) may be configuredsuch that, where the light propagation direction by the total reflectionin the inside of the second light conduction plate is represented as Ydirection and the thicknesswise direction of the second light conductionplate is represented as X direction, the light propagation direction bythe total reflection in the inside of the first light conduction plateis a Z direction and the thicknesswise direction of the first lightconduction plate is the X direction, and the beam diameter along the Zdirection of the light emitted from the first light conduction plate isgreater than the beam diameter along the Z direction of the lightincident to the first light conduction plate. It is to be noted that,where an optically reflecting element such as a mirror is disposedbetween the first light conduction plate and the second light conductionplate so that light emitted from the first light conduction plate isintroduced in a variously varied direction to the second lightconduction plate, the relationship of the X, Y and Z directions of thefirst light conduction plate to those of the second light conductionplate should be determined based on the behavior of light when it isassumed that the optical reflecting element such as a mirror is removed.This similarly applies also to the description given below. Also in theimage displaying apparatus according to the second mode of the presentinvention including the image production apparatus of the first form andthe image production apparatus of the second form (such image displayingapparatus may be hereinafter referred to generally as “image displayingapparatus according to the second mode”), the beam diameter along the Zdirection of light emitted from the entire beam expansion section isgreater than the beam diameter in the Z direction of light incident tothe beam expansion section.

The image display apparatus and so forth according to the first mode ofthe present invention including the preferred forms described above maybe configured such that the reflection type volume hologram diffractiongrating is disposed on a face of the first light conduction plateopposing to the second light conduction plate; and part of the lightincident to the first light conduction plate is diffracted by thereflection type volume hologram diffraction grating, totally reflectedonce in the inside of the first light conduction plate, totallyreflected once on the surface of the reflection type volume hologramdiffraction grating, diffracted by the reflection type volume hologramdiffraction grating and then emitted from the first light conductionplate while the remaining part of the light incident to the first lightconduction plate is emitted from the first light conduction plate afterpassing through the first light conduction plate and the reflection typevolume hologram diffraction grating. It is to be noted that such abehavior of light in the first light conduction section as describedabove is hereinafter referred to as “emission of the light from thefirst light conduction section by two times of total reflection” for theconvenience of description. The interference fringes formed on thereflection type volume hologram diffraction grating should be optimizedso that such a Bragg condition that part of the light incident to thefirst light conduction plate is diffracted by the reflection type volumehologram diffraction grating, totally reflected once in the inside ofthe first light conduction plate, totally reflected once on the surfaceof the reflection type volume hologram diffraction grating, diffractedby the reflection type volume hologram diffraction grating and thenemitted from the first light conduction plate may be satisfied.

However, the configuration of the reflection type volume hologramdiffraction grating is not limited to that described above. In otherwords, the configuration the reflection type volume hologram diffractiongrating is not limited to the configuration wherein all of part of thelight incident to the first light conduction plate is emitted from thefirst light conduction section by the emission of the light from thefirst light conduction section by two times of total reflection. Inparticular, the reflection type volume hologram diffraction grating maybe configured otherwise such that the light is totally reflected in theinside of the first light conduction plate, totally reflected on thesurface of the reflection type volume hologram diffraction grating,totally reflected in the inside of the first light conduction plateagain, totally reflected on the surface of the reflection type volumehologram diffraction grating again, diffracted by the reflection typevolume hologram diffraction grating and then emitted from the firstlight conduction plate. In other words, the reflection type volumehologram diffraction grating may be configured such that part of thepart of the light incident to the first light conduction plate isemitted by the “emission of the light from the first light conductionplate by two times of total reflection” and the remaining part of thepart of the light incident to the first light conduction plate isemitted by “emission of the light from the first light conductionsection by four times of total reflection.” Further, the reflection typevolume hologram diffraction grating may be configured otherwise suchthat emission of the light from the first light conduction section by agreater plural number of times of total reflection may occur.

Where all of the part of the light entering the first light conductionplate by the emission of the light from the first light conductionsection by two times of total reflection” is emitted, preferably thelight amount of the part of the light and the light amount of theremaining part of the light in the first light conduction plate is equalto each other from the point of view of achieving uniformity inintensity distribution of light emitted from the entire first lightconduction section. To this end, preferably

T(1−η)=(T·η)²

where η is the reflection efficiency of the reflection type volumehologram diffraction grating which composes the first light conductionsection and T is the light transmission factor of the reflection typevolume hologram diffraction grating. In particular, where T=1,preferably

η=0.62

is satisfied. In order to achieve this, optimization of selection of amaterial for forming the reflection type volume hologram diffractiongrating, optimization of the thickness of the reflection type volumehologram diffraction grating and optimization of the refractive indexmodulation degree Δn of the reflection type volume hologram diffractiongrating should be carried out.

Further, the image displaying apparatus and so forth according to thefirst mode of the present invention including the preferred forms andconfigurations described above may be structured such that the firstlight conduction section has a structure wherein the first lightconduction plate, the reflection type volume hologram diffractiongrating and a transparent parallel flat plate are laminated in orderfrom the light incidence side. In particular, that the reflection typevolume hologram diffraction grating is sandwiched by the first lightconduction plate and the transparent parallel flat plate is preferablefrom the point of view of protection of the reflection type volumehologram diffraction grating, prevention of scattering of light andprevention of a drop of the contract and deterioration of theresolution.

Alternatively, the image displaying apparatus and so forth according tothe first mode of the present invention including the preferred formsand configurations described above may be configured such that the firstdeflection section is configured from a diffraction grating element. Inthis instance, the image displaying apparatus may be configured suchthat the first deflection section is configured from a reflection typevolume hologram diffraction grating; and where the light propagationdirection by the total reflection in the inside of the second lightconduction plate is represented a Y direction and the thicknesswisedirection of the second light conduction plate is represented as Xdirection, the direction in which the interference fringes of thereflection type volume hologram diffraction grating which configures thefirst deflection section are juxtaposed, that is, the diffractiondirection, is the Y direction and the direction in which theinterference fringes of the reflection type volume hologram diffractiongrating which configures the first light conduction section arejuxtaposed, that is, the diffraction direction, is a Z direction.Further, in this instance or in such a configuration as just described,image displaying apparatus and so forth may further include a phasedifference plate disposed between the first light conduction plate andthe second light conduction plate and adapted to vary a phase differenceof polarization components outputted from the first light conductionplate. Furthermore, the image displaying apparatus may be configuredsuch that the polarized light components of the light passing throughthe phase difference plate are parallel to the Z direction, that is, thephase difference plate is disposed such that a polarized light componentof the light to enter the first deflection section becomes parallel tothe Z direction. Further, the image displaying apparatus may beconfigured such that a second phase difference plate for varying thephase difference of polarized light components emitted from thecollimate optical system or the relay optical system is disposed betweenthe collimate optical system or the relay optical system and the firstlight conduction plate. Furthermore, the image displaying apparatus maybe configured such that the polarized light components of the lightpassing through the second phase difference plate are parallel to the Ydirection, that is, the second phase difference plate is disposed suchthat a polarized light component of the light to enter the first lightconduction plate becomes parallel to the Y direction.

Alternatively, the image display apparatus and so forth according to thefirst mode or the second mode of the present invention including thepreferred forms and configurations described above may be configuredsuch that the first deflection section diffracts the light incident tothe second light conduction plate; and the second deflection sectiondiffracts the light propagated in the inside of the second lightconduction plate by total reflection over a plural number of times. Inthis instance, the image displaying apparatus and so forth may beconfigured such that the first deflection section and the seconddeflection section are individually configured from a diffractiongrating element. Furthermore, the image displaying apparatus and soforth may be configured such that the diffraction grating element isconfigured from a reflection type diffraction grating element, or thediffraction grating element is configured from a transmission typediffraction grating element, or else one of the diffraction gratingelements is configured from a reflection type diffraction gratingelement and the other one of the diffraction grating elements isconfigured from a transmission type diffraction grating element.

Or, the image display apparatus and so forth according to the first modeor the second mode of the present invention including the preferredforms and configurations described above may be configured such that thefirst deflection section reflects the light incident to the second lightconduction plate; and the second deflection section transmits andreflects the light propagated in the inside of the second lightconduction plate by total reflection over a plural number of times. Inthis instance, the image display apparatus and so forth may beconfigured such that the first deflection section functions as areflecting mirror; and the second deflection section functions as ahalf-mirror.

Meanwhile, the image display apparatus or the optical apparatusaccording to the second mode of the present invention including thepreferred forms and configurations described above may be configuredsuch that the beam expansion section is configured from a firstreflecting mirror and a second reflecting mirror;

the first reflecting mirror is positioned on the opposite side to theimage production apparatus with the light conduction section sandwichedtherebetween (in other words, positioned on the opposite side to thelight incidence side of the light conduction section); and

the second reflecting mirror is positioned adjacent the image productionapparatus with respect to the light conduction section (in other words,positioned on the light incidence side of the light conduction section).Further, in this instance, the image display apparatus or the opticalapparatus may be configured such that part of the light emerging fromthe image production apparatus repetitively undergoes, in order by apredetermined number of times, passage through the light conductionplate and the first deflection section, reflection by the firstreflecting mirror, passage through the light conduction plate and thefirst deflection section, reflection by the second reflecting mirror,and passage of part of the light through the light conduction plate andthe first deflection section.

Here, each of light reflecting faces of the first and second reflectingmirrors which configure the beam expansion section may be smooth or mayhave a plurality of convex and concave portions. In the latter case,preferably the convex and concave portions extend in planes parallel toa plane defined by an X axis and a Z axis and have a shape of acombination of adjacent sides to the right angle of a right-angledtriangle (such adjacent sides are hereinafter referred to merely as“adjacent sides”) along the Y direction when it is assumed to cut theconcave and convex portions in planes defined by normal lines to thefirst reflecting mirror and the second reflecting mirror and a Y axis.In particular, each of the convex and concave portions preferablyextends in parallel to the plane defined by the X axis and the Z axisand has a shape of a right-angular prism having a vertical angle of 90degrees. It is to be noted that a reflecting mirror of the typedescribed is also called reversal mirror. The right-angle triangle maybe a right-angled isosceles triangle having adjacent sides which areequal in length to each other or a right-angled triangle having adjacentsides which are different from each other. In particular, adjacent sidesof right-angled triangles of the same shape may be juxtaposed along theY direction or adjacent sides of right-angled triangles of differentshapes may be juxtaposed along the Y direction. In particular, in theformer case, each of the convex and concave portions may be configuredsuch that, for example, the adjacent sides of the right-angled isoscelestriangles are juxtaposed. On the other hand, in the latter case, each ofthe convex and concave portions may be configured such that, forexample, the adjacent sides of each right-angled isosceles triangle arejuxtaposed on the central region of the light reflecting face, theadjacent sides of each right-angled scalene triangle are juxtaposed onthe right side of a central region of the light reflecting face whilethe adjacent sides of each of the right-angled scalene trianglessymmetrical to those on the right side of the central region of thelight reflecting face are juxtaposed on the left side of the centralregion of the light reflecting face.

Here, an edge line of the light reflecting face corresponding to theright angle of the right-angled triangle extends in parallel to theplane defined by the X axis and the Z axis. For the convenience ofdescription, the two inclined faces of the light reflecting facecorresponding to the adjacent sides to the right angle of a right-angledtriangle are hereinafter referred to individually as “first inclinedface” and “second inclined face.” Light incoming to the first reflectingmirror collides with and is reflected by the first inclined face andthen collides with and is reflected by the second inclined face,whereafter it emerges from the first reflecting mirror. Or, lightincoming to the first reflecting mirror collides with and is reflectedby the second inclined face and then collides with and is reflected bythe first inclined face, whereafter it emerges from the first reflectingmirror. The light incoming to the first inclined face and the lightemerging from the second inclined face are parallel. Similarly, lightincoming to the second reflecting mirror collides with and is reflectedby the first inclined face and then collides with and is reflected bythe second inclined face, whereafter it emerges from the secondreflecting mirror. Or, light incoming to the first reflecting mirrorcollides with and is reflected by the second inclined face and thencollides with and is reflected by the first inclined face, whereafter itemerges from the first reflecting mirror. The light incoming to thefirst inclined face and the light emerging from the second inclined faceare parallel. Although reflection of light is repeated between the firstreflecting mirror and the second reflecting mirror, the colliding pointof the light flux with the first reflecting mirror and the collidingpoint of the light flux with the second reflecting mirror do not move inthe Y direction in principle but merely move in the X direction and theZ direction. Therefore, the necessity to set the diameter of theaperture stop in the Y direction of the image production apparatus to agreat diameter is eliminated.

It is to be noted that, where the light reflecting faces of the firstreflecting mirror and the second reflecting mirror are smooth, a lightreflecting layer is provided on the light reflecting faces. Meanwhile,where each of the light reflecting faces of the first reflecting mirrorand the second reflecting mirror has a plurality of convex and concaveportions, a light reflecting layer may be or may not be provided on thelight reflecting face. In the former case, light can be reflectedwithout allowing the light to be admitted into the inside of the firstreflecting mirror and the second reflecting mirror. Alternatively, lightcan be reflected by allowing the light to be admitted into the inside ofthe first reflecting mirror and the second reflecting mirror. On theother hand, in the latter case, light should be introduced into theinside of the first reflecting mirror and the second reflecting mirrorso that light is totally reflected by the first inclined face and thesecond inclined face.

Alternatively, the image display apparatus or the optical apparatusaccording to the second mode of the present invention including thepreferred forms and configurations described above may be configuredsuch that the beam expansion section is configured from a half-mirrorand a reflecting mirror; and the half-mirror and the reflecting mirrorare positioned adjacent the image production apparatus with respect tothe light conduction section (in other words, positioned on the lightincidence side of the light conduction section). Further, in thisinstance, the image displaying apparatus or the optical apparatus may beconfigured such that part of the light emitted from the image productionapparatus passes through the half-mirror and introduced into the lightconduction plate and the remaining part of the light is reflected on thehalf-mirror and introduced into the reflecting mirror, and part of thelight reflected on the reflecting mirror passes through the half-mirrorand introduced into the light conduction plate while the remaining partof the light is reflected on the half-mirror and introduced into thereflecting mirror; the passage and reflection actions being repetitivelycarried out by a predetermined number of times.

The image formation apparatus of the image production apparatus in thefirst mode may be, for example, an image formation apparatus whichincludes a reflection type spatial light modulation apparatus and alight source, another image information apparatus which includes atransmission type spatial light modulation apparatus and a light sourceor a further image formation apparatus which includes light emittingelements such as organic EL (Electro Luminescence) elements, inorganicEL elements or light emitting diodes (LEDs). Among them, the imageformation apparatus which includes a reflection type spatial lightmodulation apparatus and a light source is used preferably. The spatiallight modulation apparatus may be, for example, a liquid crystal displayapparatus of the transmission type or the reflection type which includeslight valves such as, for example, LCOS (Liquid Crystal On Silicon)light valves or a digital micromirror device (DMD), and the light sourcemay be a light emitting element. Further, the reflection type spatiallight modulation apparatus may include a liquid crystal displayapparatus, and a beam splitter for reflecting part of light from a lightsource so as to be introduced to the liquid crystal display apparatusand passing part of the light reflected by the liquid crystal displayapparatus therethrough so as to be introduced to the collimator opticalsystem. The light emitting element which forms the light source may be ared light emitting element, a green light emitting element, a blue lightemitting element or a white light emitting element. Further, the lightemitting element may be, for example, a semiconductor laser element, asolid-state laser or an LED. The number of pixels may be determinedbased on specifications required for the image displaying apparatus. Theparticular value of the number of pixels may be 320×240, 432×240,640×480, 854×480, 1024×768 or 1920×1080. The collimate optical systemhas a function of converting position information of a pixel into angleinformation of the optical system of the second light conductionsection. The collimate optical system may be a convex lens, a concavelens, a free-form surface prism or a hologram lens which are used singlyor in combination so that the optical system may have a positive opticalpower as a whole.

Meanwhile, the light source of the image production apparatus in thesecond mode may be a light emitting element and particularly a red lightemitting element, a green light emitting element, a blue light emittingelement or a white light emitting element. Further, the light emittingelement may be, for example, a semiconductor laser element, asolid-state laser or an LED. The number of pixels or virtual pixels ofthe image displaying apparatus of the second mode may be determinedbased on specifications required for the image displaying apparatus. Theparticular value of the number of pixels or virtual pixels may be320×240, 432×240, 640×480, 854×480, 1024×768 or 1920×1080. Where thelight source is formed from a red light emitting element, a green lightemitting element and a blue light emitting element, preferably, forexample, a cross prism is used to carry out color synthesis. Thescanning section carries out horizontal scanning and vertical scanningof the light emitted from the light source. For example, a MEMS (MicroElectro Mechanical System) having micromirrors rotatable intwo-dimensional directions or a galvano mirror may be used. The relayoptical system may be formed from a well-known relay optical system.

For example, as an image formation apparatus or a light source which isconfigured from a light emitting element and a light valve, thefollowing configurations may be applied in addition to a backlight whichgenerally emits white light and a liquid crystal display apparatus whichincludes red light emitting elements, green light emitting elements andblue light emitting elements.

Image Formation Apparatus A

The image formation apparatus A includes:

(α) a first image formation apparatus which includes a first lightemitting panel wherein a plurality of first light emitting elements foremitting blue light are arrayed in a two-dimensional matrix;(β) a second image formation apparatus which includes a second lightemitting panel wherein a plurality of second light emitting elements foremitting green light are arrayed in a two-dimensional matrix;(γ) a third image formation apparatus which includes a third lightemitting panel wherein a plurality of third light emitting elements foremitting red light are arrayed in a two-dimensional matrix; and(δ) a section configured to integrate light emitting from the first,second and third image formation apparatus into a single light flux(such means may be a dichroic prism; this similarly applies also in thefollowing description), and

the light emitting/no-light emitting state of each of the first, secondand third light emitting elements is controlled.

Image Formation Apparatus B

The image formation apparatus B includes:

(α) a first image formation apparatus which includes a first lightemitting element for emitting blue light, and a first light passagecontrolling apparatus for controlling passage/non-passage therethroughof the emitted light emitted from the first light emitting element foremitting blue light (the first light passage controlling apparatus is akind of light valve which is formed, for example, from a liquid crystaldisplay device, a digital micromirror device (DMD) or an LCOS device;this similarly applies also in the following description);(β) a second image formation apparatus which includes a second lightemitting element for emitting green light, and a second light passagecontrolling apparatus (light valve) for controlling passage/non-passagetherethrough of the emitted light emitted from the second light emittingelement for emitting green light;(γ) a third image formation apparatus which includes a third lightemitting element for emitting red light, and a third light passagecontrolling apparatus (light valve) for controlling passage/non-passagetherethrough of the emitted light emitted from the third light emittingelement for emitting red light; and(δ) a section configured to integrate the light passing through thefirst, second and third light passage controlling apparatus into asingle light flux, and

the passage/non-passage of the emitted light emitted from the lightemitting elements is controlled by the light passage controllingapparatus to display an image. As a section (material) for conductingthe emitted light emitted from the first, second and third lightemitting elements to the light passage controlling apparatus, a lightconduction member, a microlens array, a mirror, a reflecting plate or acondensing lens may be used.

Image Formation Apparatus C

The image formation apparatus C includes:

(α) a first image formation apparatus which includes a first lightemitting panel wherein a plurality of first light emitting elements foremitting blue light are arrayed in a two-dimensional matrix and a bluelight passage controlling apparatus (light valve) for controllingpassage/non-passage of the emitted light emitted from the first lightemitting panel;(β) a second image formation apparatus which includes a second lightemitting panel wherein a plurality of second light emitting elements foremitting green light are arrayed in a two-dimensional matrix and a greenlight passage controlling apparatus (light valve) for controllingpassage/non-passage of the emitted light emitted from the second lightemitting panel;(γ) a third image formation apparatus which includes a third lightemitting panel wherein a plurality of third light emitting elements foremitting red light are arrayed in a two-dimensional matrix and a redlight passage controlling apparatus (light valve) for controllingpassage/non-passage of the emitted light emitted from the third lightemitting panel; and(δ) a section configured to integrate the light passing through theblue, green and red light passage controlling apparatus into a singlelight flux, and

the passage/non-passage of the emitted light emitted from the first,second and third light emitting panels is controlled by the lightpassage controlling apparatus (light valve) to display an image.

Image Formation Apparatus D

The image formation apparatus D is a color display image formationapparatus of the field sequential type and includes:

(α) a first image formation apparatus including a first light emittingelement for emitting blue light;(β) a second image formation apparatus including a second light emittingelement for emitting green light;(γ) a third image formation apparatus including a third light emittingelement for emitting red light;(δ) a section configured to integrate the light emitted from the first,second and third image formation apparatus into a single light flux; and(∈) a light passage controlling apparatus (light valve) for controllingpassage/non-passage of the emitted light emitted from the integratingsection, and

the passage/non-passage of the emitted light emitted from the lightemitting elements is controlled by the light passage controllingapparatus to display an image.

Image Formation Apparatus E

Also the image formation apparatus E is a color display image formationapparatus of the field sequential type and includes:

(α) a first image formation apparatus including a first light emittingpanel wherein a plurality of first light emitting elements for emittingblue light are arrayed in a two-dimensional matrix;(β) a second image formation apparatus including a second light emittingpanel wherein a plurality of second light emitting elements for emittinggreen light are arrayed in a two-dimensional matrix;(γ) a third image formation apparatus including a third light emittingpanel wherein a plurality of third light emitting elements for emittingred light are arrayed in a two-dimensional matrix;(δ) a section configured to integrate the light emitted from the first,second and third image formation apparatus into a single light flux; and(∈) a light passage controlling apparatus (light valve) for controllingpassage/non-passage of the emitted light emitted from the integratingsection, and

the passage/non-passage of the emitted light emitted from the lightemitting panels is controlled by the light passage controlling apparatusto display an image.

Image Formation Apparatus F

The image formation apparatus F is a color display image formationapparatus of the passive matrix type or the active matrix type whereinthe light emission/no-light emission state of each of first, second andthird light emitting elements is controlled to display an image.

Image Formation Apparatus G

The image information apparatus G is a color display image formationapparatus of the field sequential type which includes a light passagecontrolling apparatus (light valve) for controlling passage/non-passageof emitted light emitted from light emitting element units arrayed in atwo-dimensional matrix. The light emission/no-light emission state ofeach of first, second and third light emitting elements in each lightemitting element unit is time-divisionally controlled. Further, thelight passage controlling apparatus controls passage/non-passage of theemitted light emitted from the first, second and third light emittingelements to display an image.

In a preferred configuration of the image production apparatus in thefirst or second form, the first deflection section functions as areflecting mirror and the second deflection section functions as ahalf-mirror as described hereinabove. In such a form as just described,the first deflection section, or the reflecting mirror which forms thebeam expansion section, can be formed from a light reflecting film,which is a kind of mirror, made of, for example, a metal including analloy for reflecting light incident to the second light conduction plateor a diffraction grating (for example, a hologram diffraction gratingfilm) for diffracting light incident to the second light conductionplate. Meanwhile, the second deflection section, or the half-mirrorwhich forms the beam expansion section, can be formed, for example, froma dielectric multilayer film, a half-mirror, a polarized light beamsplitter or a hologram diffraction grating film. The first and seconddefection sections are disposed in the inside of the second lightconduction plate, that is, incorporated in the inside of the secondlight conduction plate. Thus, the first defection section reflects ordiffracts parallel light incident to the second light conduction plateso that the parallel light incident to the second light conduction plateis totally reflected in the inside of the second light conduction plate.Meanwhile, the second deflection section reflects or diffracts theparallel light propagated in the inside of the second light conductionplate by total reflection by a plural number of times and emits thereflected or diffracted light in the form of parallel light from thesecond light conduction plate.

Alternatively, in another preferred configuration of the imageproduction apparatus in the first or second form, the first and seconddeflection sections are formed, for example, from a reflection typediffraction grating element, particularly, for example, from areflection type volume hologram diffraction grating as describedhereinabove. It is to be noted that the first deflection section formedfrom a reflection type volume hologram diffraction grating ishereinafter referred to sometimes as “first diffraction grating member”and the second deflection section formed from a reflection type volumehologram diffraction grating is hereinafter referred to sometimes as“second diffraction grating member” for the convenience of description.

In order to make the first or second diffraction grating member readyfor diffraction reflection of P (here P=3 for red, green and blue)different kinds of light having P different wavelength bands orwavelengths, it can be formed by laminating P diffraction grating layerseach formed from a reflection type volume hologram diffraction grating.In each diffraction grating layer, interference fringes corresponding toone frequency band or frequency are formed. Alternatively, in order tomake the first or second diffraction grating member ready fordiffraction reflection of P different kinds of light having P differentwavelength bands or wavelengths, it may be configured such that thefirst or second diffraction grating member formed from a singlediffraction grating layer has p kinds of interference fringes formedtherein. Or it is possible to adopt a different configuration wherein anangle of view is divided, for example, equally into three angles and thefirst or second diffraction grating member is formed by laminatingdiffraction grating layers corresponding to the divisional angles ofview. By adopting any of the configurations described, it is possible toachieve increase of the diffraction efficiency, increase of thediffraction reception angle and optimization of the diffraction anglewhen light having each wavelength band or wavelength is diffracted andreflected by the first or second diffraction grating member. Also thereflection type volume hologram diffraction grating of the first lightconduction section may be configured similarly.

The first and second diffraction grating members may be formed from aphotopolymer material. The material and the basic structure of the firstand second diffraction grating members each formed from a reflectiontype volume hologram diffraction grating may be same as those of anexisting reflection type volume hologram diffraction grating. Thereflection type volume hologram diffraction grating signifies a hologramdiffraction grating which diffracts and reflects only + first orderdiffraction light. While the diffraction grating member has interferencefringes formed from the inside to the surface thereof, the formationmethod of such interference fringes may be same as a traditionalformation method. In particular, for example, object light is irradiatedupon a member of a photopolymer material, which forms the diffractiongrating member, from a first predetermined direction on one side whilereference light is simultaneously irradiated upon the member, whichforms the diffraction grating member, from a second predetermineddirection on the opposite side. Then, interference fringes formed by theobject light and the reference light are recorded in the inside of themember which forms the diffraction grating member. If the firstpredetermined direction, the second predetermined direction and thewavelengths of the object light and the reference light are selectedappropriately, then a desired pitch of the interference fringes on thesurface of the diffraction grating member and a diffraction inclinationangle or slant angle of the interference fringes can be obtained. Theinclination angle of interference fringes signifies an angle defined bythe surface of the diffraction grating member or diffraction gratinglayer and the interference fringes. Where the first and seconddiffraction grating members are formed from a lamination structure of Pdiffraction grating layers each formed from a reflection type volumehologram diffraction grating, the P diffraction grating layers may firstbe produced separately from each other and then laminated or adheredusing, for example, an ultraviolet curing bonding agent. Or, the Pdiffraction grating layers may be produced otherwise by producing asingle diffraction grating layer using a photopolymer material havingself-bonding properties and then successively adhering a photopolymermaterial having self-bonding properties. The reflection type volumehologram diffraction grating which forms the first light conductionsection may be configured similarly.

While, in the image production apparatus of the first or second form,light formed as a plurality of parallel light fluxes by the collimateoptical system or the relay optical system is introduced into the secondlight conduction plate, the request for such parallel light is based onthe fact that light wave information when such light is introduced intothe second light conduction plate need to be maintained also after thelight is emitted from the second light conduction plate through thefirst and second deflection sections. It is to be noted that, in orderto produce a plurality of parallel light fluxes, particularly a lightemitting portion of the image formation apparatus should be positionedat the position of a focal length of, for example, the collimate opticalsystem or the relay optical system. The collimate optical system has afunction of converting position information of a pixel into angleinformation in the optical system of the optical apparatus.

In the image display apparatus, the second light conduction plate hastwo parallel faces, that is, a first face and a second face, extendingin parallel to the light propagation direction, that is, to the Ydirection, by internal total reflection in the second light conductionplate. Where the face of the second light conduction plate through whichlight enters is a second light conduction plate incidence face and theface of the second light conduction plate from which light emerges is asecond light conduction plate emergence face, the second lightconduction plate incidence face and the second light conduction plateemergence face may be formed from the first face. Or, the second lightconduction plate incidence face may be formed from the first face whilethe second light conduction plate emergence face is formed from thesecond face.

The second light conduction plate, first light conduction plate ortransparent parallel flat plate may be formed from any of such materialsas glass including quartz glass and optical glass such as BK7, andplastics materials such as PMMA, polycarbonate resins, acrylic-basedresins, amorphous polypropylene-based resins and styrene-based resinsincluding AS resins. The shape of the second light conduction plate isnot limited to the flat shape but may be a curved shape.

The image display apparatus of the present invention can be used toconfigure, for example, a head-mounted type display (HMD) unit and iseffective to achieve reduction in weight and size of the apparatus.Further, a disagreeable feeling when the apparatus is mounted can bereduced significantly, and besides the production cost can be reduced.

The head-mounted type display unit includes:

(1) a frame of the glasses type for being mounted on the head of anobserver; and

(2) an image display apparatus of the present invention.

The head-mounted type display unit may include one image displayapparatus of the present invention (monocular type) or two image displayapparatus of the present invention (binocular type).

The frame includes a front portion disposed in front of the observer,two temple portions attached for pivotal motion to the opposite ends ofthe front portion by hinges, and two modern portions attached to endportions of the temple portions, and further includes nose pads. Wherethe entire head-mounted type display unit is viewed, the assembly of theframe and the nose pads has a structure substantially same as that ofordinary glasses except that it does not have a rim. The frame may beformed from a material same as that used for configuration of ordinaryglasses such as a metal, an alloy, a plastic material or a suitablecombination of such materials. Also the nose pads may be formed in awell-known configuration and structure.

Further, from a point of view of the design of the head-mounted typedisplay unit or of easiness of mounting of the head-mounted type displayunit, the head-mounted type display unit is formed preferably such thatwiring lines such as a signal line and a power supply line from one ortwo image production apparatus extend through the temple portions andthe inside of the modern portions and outwardly from the end portions ofthe modern portions and are connected to an external circuit which maybe a controlling circuit. Further, each image production apparatusincludes a headphone section, and the head-mounted type display unit isconfigured further preferably such that headphone wiring lines from theimage production apparatus extend through the temple portions and theinside of the modern portions and further from the end portions of themodern portions to the headphone sections. The headphone sections maybe, for example, those of the inner ear type or those of the canal type.More particularly, the headphone section wiring lines are preferablyconfigured such that they extend from the end portions of the modernportions to the headphone sections in such a manner as to go round therear side of the auricles or ear capsules.

The head-mounted type display unit may be formed such that an imagepickup apparatus is attached to a central portion of the front portion.The image pickup apparatus particularly includes a solid-state imagepickup element formed, for example, from a CCD sensor or a CMOS sensor,and a lens. Wiring lines from the image pickup apparatus may, forexample, extend along the rear face of the front portion and beconnected to one of the image displaying apparatus. Further, the wiringlines may be included in the wiring lines extending from the imageproduction apparatus.

Where the head-mounted type display unit is formed as that of thebinocular type, preferably it is configured such that

the second light conduction section is disposed as a whole on the centerside of the face of the observer with respect to the image productionapparatus; that

the head-mounted type display unit further includes a coupling memberfor coupling the two image displaying apparatus to each other; that

the coupling member is attached to the side, which opposes to theobserver, of a central portion of the frame positioned between the twopupils of the observer; and that

a projection image of the coupling member is included in a projectionimage of the frame.

If the head-mounted type display unit is structured such that thecoupling member is attached to the central portion of the framepositioned between the two pupils of the observer in this manner, thatis, where the image display apparatus are not attached directly to theframe, then when the observer mounts the frame on the head thereof, thetemple portions are placed into an outwardly expanded state. As aresult, even if the frame is deformed, such deformation of the framedoes not cause displacement or positional variation of the imagereproduction apparatus or of the second light conduction section, oreven if the deformation causes such displacement, the amount of suchdisplacement is very small. Therefore, such a situation that the angleof convergence of the left and right images varies can be prevented withcertainty. Besides, since there is no necessity to raise the rigidity ofthe front portion of the frame, increase in weight of the frame,degradation in design performance and increase of the cost are notencountered. Further, since the image displaying apparatus are notattached directly to the frame of the glasses type, the design, colorand so forth of the frame can be selected freely depending upon theliking of the observer, and also the restriction to the design of theframe is little and the degree of freedom in design is high. Inaddition, the coupling member is disposed between the observer and theframe, and besides a projection image of the coupling member is includedin a projection image of the frame. In other words, when thehead-mounted type display unit is observed from the front of theobserver, the coupling member is hidden by the frame. Accordingly, highdesign performances can be provided to the head-mounted type displayunit.

It is to be noted that the coupling member is attached preferably to theface of the central portion of the front portion thereof which ispositioned between the two pupils of the observer. The central portionof the front portion corresponds to a bridging portion of ordinaryglasses.

Although the two image displaying apparatus are coupled to each other bythe coupling member, particularly the image production apparatus areattached preferably to end portions of the coupling member such that theattachment state thereof can be adjusted. In this instance, each imageproduction apparatus is preferably positioned on the outer side withrespect to the pupils of the observer. Further, in such a configurationas just described, where the distance between the attached portioncenter of one of the image production apparatus and an end portion ofthe frame is represented by α, the distance from the center of thecoupling member to the end portion of the frame by β, the distancebetween the attached portion center of the other image productionapparatus and the end portion of the frame by γ, and the length of theframe by L, 0.01×L≦α≦0.30×L is satisfied. Preferably, 0.05×L≦α≦0.25×L issatisfied. Further, 0.35×L≦β≦0.65×L is satisfied, and preferably,0.45×L≦β≦0.55×L is satisfied. Furthermore, 0.70×L≦γ≦0.99×L is satisfied,and preferably, 0.75×L≦γ≦0.95×L is satisfied. The attachment of theimage production apparatus to the opposite end portions of the couplingmember is carried out in the following manner. In particular, forexample, three through-holes are provided at different locations of eachend portion of the coupling member, and threaded portions correspondingto the through-holes are provided on each image production apparatus.Then, a screw is inserted into each through-hole and screwed into acorresponding one of the threaded portions provided on the imageproduction apparatus. A spring is inserted in advance between the screwand the threaded-portion. Thus, the mounted state of the imageproduction apparatus, that is, the inclination of the image productionapparatus with respect to the coupling member, can be adjusted by thetightened state of the screws.

Here, the attachment portion center of an image production apparatus isa bisecting point, along an axial direction of the frame, of a portionof a projection image of the frame with which a projection image of theimage production apparatus which is obtained when the image productionapparatus and the frame are projected to a virtual plane in a statewherein the image production apparatus is attached to the couplingmember overlaps. Further, the center of the coupling member is abisecting point, along the axial direction of the frame, of a portion ofthe coupling member at which the coupling member contacts with the framein the state wherein the coupling member is attached to the frame. Thelength of the frame where the frame is curved is a length of theprojection image of the frame. It is to be noted that the projectiondirection is a perpendicular direction to the face of the observer.

Alternatively, the head-mounted type display unit may be formed suchthat, although the two image displaying apparatus are coupled to eachother by the coupling member, particularly the coupling member couplesthe two second light conduction sections to each other. It is to benoted that the two second light conduction sections are sometimesproduced as a unitary member. In such an instance, the coupling memberis attached to the integrally produced second light conduction sections,and also this coupling form is included in the form wherein the couplingmember couples the two second light conduction sections to each other.Where the distance between the center of one of the image productionapparatus and one end portion of the frame is represented by α′ and thedistance between the center of the other image production apparatus andthe one end portion of the frame is represented by γ′, also the valuesof α′ and γ′ are preferably equal to those of α and γ specifiedhereinabove, respectively. It is to be noted that the center of an imageproduction apparatus is a bisecting point, along an axial direction ofthe frame, of a portion of a projection image of the frame with which aprojection image of the image production apparatus which is obtainedwhen the image production apparatus and the frame are projected to avirtual plane in a state wherein the image production apparatus isattached to the second light conduction section overlaps.

The shape of the coupling member can essentially be determinedarbitrarily as far as the projection image of the coupling member isincluded in the projection image of the frame, and, for example, thecoupling member may have a shape of a bar or an elongated plate. Alsothe material of the coupling member may be a metal, an alloy, a plasticmaterial or a suitable combination of such materials.

Embodiment 1

An embodiment 1 relates to the image displaying apparatus according tothe first mode of the present invention and the optical apparatusaccording to the first mode of the present invention and further relatesto the image production apparatus of the first form. The imagedisplaying apparatus according to the embodiment 1 and embodiments 2 to4 hereinafter described are conceptually shown in FIGS. 1, 2, 3A and 4,respectively. Further, an arrangement state of the image productionapparatus, a first light conduction section and a second lightconduction section is schematically shown in FIG. 5A, and a concept whenthe first light conduction section is cut is illustrated in FIG. 5B.

The image displaying apparatus 100, 200, 300 or 400 according to theembodiment 1 or any of the embodiments 2 to 4 hereinafter describedincludes

(A) an image production apparatus 110 or 210;

(B) a first light conduction section 120 adapted to receive, conduct andemit the light emitted from the image production apparatus 110 or 210;and

(C) a second light conduction section 130 or 330 adapted to receive andconduct light emitted from the first light conduction section 120 andthen emit the light toward the pupil 41 of an observer 40. The firstlight conduction section 120 includes:

(B-1) a first light conduction plate 121 for propagating part of theincident light by total reflection in the inside thereof and emittingthe propagated light therefrom;

(B-2) a reflection type volume hologram diffraction grating 122 disposedon the first light conduction plate 121. Meanwhile, the second lightconduction section 130 or 330 includes:

(C-1) a second light conduction plate 131 or 331 adapted to propagateincoming light in the inside thereof by total reflection and then emitthe light;

(C-2) a first deflection section 140 or 340 disposed on the second lightconduction plate 131 or 331 and adapted to deflect light incident to thesecond light conduction plate 131 or 331 such that the light introducedto the second light conduction plate 131 or 331 is totally reflected inthe inside of the second light conduction plate 131 or 331; and

(C-3) a second deflection section 150 or 350 disposed on the secondlight conduction plate 131 or 331 and adapted to deflect the lightpropagated in the inside of the second light conduction plate 131 or 331by total reflection over a plural number of times in order to emit thelight propagated in the inside of the second light conduction plate 131or 331 by total reflection from the second light conduction plate 131 or331. It is to be noted that the second light conduction section 130 or330 is of the see-through type or half-transmission type.

Meanwhile, the optical apparatus in the embodiment 1 or any of theembodiments 2 to 4 hereinafter described includes:

a first light conduction section 120 adapted to receive, conduct andemit a light flux; and

a second light conduction section 130 or 330 adapted to receive andconduct the light flux emitted from the first light conduction section120 and then emit the light.

The first light conduction section 120 includes:

(a-1) a first light conduction plate for propagating part of theincident light by total reflection in the inside thereof and emittingthe propagated light therefrom; and

(a-2) a reflection type volume hologram diffraction grating 122 disposedon the first light conduction plate 121, and

the second light conduction section 130 or 330 includes:

(b-1) a second light conduction plate 131 or 331 adapted to propagateincoming light in the inside thereof by total reflection and then emitthe light;

(b-2) a first deflection section 140 or 340 disposed on the second lightconduction plate 131 or 331 and adapted to deflect light incident to thesecond light conduction plate 131 or 331 such that the light introducedto the second light conduction plate 131 or 331 is totally reflected inthe inside of the second light conduction plate 131 or 331; and

(b-3) a second deflection section 150 or 350 disposed on the secondlight conduction plate 131 or 331 and adapted to deflect the lightpropagated in the inside of the second light conduction plate 131 or 331by total reflection over a plural number of times in order to emit thelight propagated in the inside of the second light conduction plate 131or 331 by total reflection from the second light conduction plate 131 or331.

Here, in the image displaying apparatus 100 or 300 of the embodiment 1or the embodiment 3 which is hereinafter described, the image productionapparatus 110 includes:

(A-1) an image formation apparatus 111 having a plurality of pixelsarrayed in a two-dimensional matrix; and

(A-2) a collimate optical system 112 for converting light emitted fromthe pixels of the image formation apparatus 111 into parallel light; and

a light flux of the parallel light obtained by the conversion by thecollimate optical system 112 is introduced to the first light conductionsection 120.

The first deflection section 140 and the second deflection section 150are disposed in the inside of the second light conduction plate 131. Thefirst deflection section 140 reflects light entering the second lightconduction plate 131, and the second deflection section 150 passes andreflects the light propagated in the inside of the second lightconduction plate 131 by total reflection by a plural number of times. Inother words, the first deflection section 140 functions as a reflectingmirror, and the second deflection section 150 functions as a halfmirror. More particularly, the first deflection section 140 provided inthe inside of the second light conduction plate 131 is formed from alight reflecting mirror which is a kind of mirror made of aluminum forreflecting light entering the second light conduction plate 131.Meanwhile, the second deflection section 150 provided in the inside ofthe second light conduction plate 131 is formed from a multilayerlaminated structure wherein a large number of dielectric laminate filmsare laminated. The dielectric laminate films are formed, for example,from a TiO₂ film as a high dielectric constant material and a SiO₂ filmas a low dielectric constant material. A multilayer laminated structurewherein a large number of dielectric laminate films are laminated isdisclosed in JP-T-2005-521099. While, in FIGS. 1 and 2, a dielectriclaminate film of six layers is shown, the number of layers of thedielectric laminate film is not limited to this. Between adjacent onesof the dielectric laminate films, a thin piece made of a material sameas that of the second light conduction plate 131 is sandwiched. It is tobe noted that, by the first deflection section 140, parallel lightentering the second light conduction plate 131 is reflected or refractedso that the incident parallel light may be totally reflected in theinside of the second light conduction plate 131. On the other hand, bythe second deflection section 150, parallel light propagated in theinside of the second light conduction plate 131 by total reflection isreflected or diffracted by a plural number of times and emitted in theform of parallel light from the second light conduction plate 131.

The first deflection section 140 may be formed by cutting away a portion134 of the second light conduction plate 131 at which the firstdeflection section 140 is to be provided to provide an inclined face atwhich the first deflection section 140 is to be formed on the secondlight conduction plate 131, forming a light reflecting film on theinclined face by vapor deposition and adhering the cut away portion 134of the second light conduction plate 131 back to the first deflectionsection 140. Meanwhile, the second deflection section 150 may be formedby producing a multilayer laminate structure wherein a large number oflayers of a material such as the material of the second light conductionplate 131 such as, for example, glass and a large number of dielectriclaminated films, which can be formed, for example, by vapor deposition,are laminated, cutting away a portion 135 of the second light conductionplate 131 at which the second deflection section 150 is to be providedto form an inclined face, adhering the multilayer laminate structure tothe inclined face, and carrying out polishing to put the profile inorder. The second light conduction section 130 wherein the firstdeflection section 140 and the second deflection section 150 areprovided in the second light conduction plate 131 can be obtained inthis manner.

In the embodiment 1 or the embodiment 3 which is hereinafter described,the image formation apparatus 111 includes a reflection type spatialoptical modulation apparatus 160 and a light source 163 which is formedfrom a light emitting diode which emits white light. More particularly,the reflection type spatial optical modulation apparatus 160 includes aliquid crystal display (LCD) apparatus 161 formed from an LCOS as alight valve, and a polarized light beam splitter 162 for reflecting apart of the light from the light source 163 to introduce the light tothe liquid crystal display apparatus 161, and passing part of the lightreflected by the liquid crystal display apparatus 161 therethrough so asto be introduced to the collimate optical system 112. The liquid crystaldisplay apparatus 161 includes a plurality of, for example, 320×240,pixels or liquid crystal cells arrayed in a two-dimensional matrix. Thepolarized light beam splitter 162 has a known configuration andstructure. Non-polarized light emitted from the light source 163collides with the polarized light beam splitter 162. The polarized lightbeam splitter 162 passes a P polarized light component of the incidentlight therethrough and emits the same to the outside of the system. Onthe other hand, an S polarized light component of the incident light isreflected by the polarized light beam splitter 162 and enters the liquidcrystal display apparatus 161. Then, the S polarized light component isreflected in the inside of the liquid crystal display apparatus 161 andthen emitted from the liquid crystal display apparatus 161. Here, of thelight emitted from the liquid crystal display apparatus 161, lightemitted from a pixel which displays “white” includes much P polarizedlight component, and light emitted from another pixel which displays“black” includes much S polarized light component. Accordingly, the Ppolarized light component from within the light emitted from the liquidcrystal display apparatus 161 and colliding with the polarized lightbeam splitter 162 passes through the polarized light beam splitter 162and are introduced to the collimate optical system 112. Meanwhile, the Spolarized light component is reflected by the polarized light beamsplitter 162 and returned to the light source 163. The liquid crystaldisplay apparatus 161 includes a plurality of, for example, 320×240,pixels (the number of liquid crystal cells is equal to three times thenumber of pixels) arrayed in a two-dimensional matrix. The collimateoptical system 112 is formed, for example, from a convex lens, and theimage formation apparatus 111, more particularly, the liquid crystaldisplay apparatus 161, is disposed at the position of a focal length ofthe collimate optical system 112 in order to produce parallel light.Meanwhile, one pixel is formed from a red light emitting subpixel foremitting red light, a green light emitting subpixel for emitting greenlight and a blue light emitting subpixel for emitting blue light.

Here, in the embodiment 1 or in any of the embodiments 2 to 4, thesecond light conduction plate 131 or 331 made of an optical glass orplastic material has two parallel faces (first face 132 or 332 andsecond face 133 or 333) extending in parallel to a light propagationdirection, that is, in a Y direction, by internal total reflection ofthe second light conduction plate 131 or 331. The first face 132 or 332and the second face 133 or 333 oppose to each other. Parallel lightenters through the first face 132 or 332 which corresponds to a lightincident face and propagates by total reflection in the inside of thesecond light conduction plate 131 or 331, whereafter it is emitted fromthe first face 132 or 332 which corresponds to a light emergent face. Itis to be noted that the light incident face and the light emergent faceare not limited to them but the light incident face may be formed fromthe second face 133 or 333 and the light emergent face may be formedfrom the first face 132 or 332.

In order to make the reflection type volume hologram diffraction grating122, which forms the first light conduction section 120, ready fordiffraction reflection of P (here P=3 for red, green and blue) differentkinds of light having P different wavelength bands or wavelengths, thereflection type volume hologram diffraction grating 122 is formed bylaminating P diffraction grating layers each formed from a reflectiontype volume hologram diffraction grating. It is to be noted that, ineach diffraction grating layer made of a photopolymer material,interference fringes corresponding to one frequency band or frequencyare formed, and the diffraction grating layers are produced by ahitherto known method. More particularly, the reflection type volumehologram diffraction grating 122 has a structure wherein a diffractiongrating layer for diffracting and reflecting red light, anotherdiffraction grating layer for diffracting and reflecting green light anda further diffraction grating layer for diffracting and reflecting bluelight are laminated. The pitch of the interference fringes formed on thediffraction grating layers or diffraction optical elements is fixed, andthe interference fringes have a linear form and extend in parallel tothe Y direction. It is to be noted that the reflection type volumehologram diffraction grating 122 is shown with a single layer. Adoptionof such a configuration as just described can achieve increase of thediffraction efficiency, increase of the diffraction reception angle andoptimization of the diffraction angle when light having the frequencybands or frequencies is diffracted and reflected by the reflection typevolume hologram diffraction grating 122. It is to be noted that also afirst diffraction grating member 340 and a second diffraction gratingmember 350 hereinafter described may be configured similarly.

Here, where the light propagation direction by internal total reflectionin the second light conduction plate 131 or 331 is defined as Ydirection and the thicknesswise direction of the second light conductionplate 131 or 331 is defined as X direction, the light propagationdirection by internal total reflection of the first light conductionplate 121 is a Z direction and the thicknesswise direction of the firstlight conduction plate 121 is the X direction. Then, the beam diameteralong the Z direction of light emitted from the first light conductionplate 121 is greater than the beam diameter along the Z direction oflight incident to the first light conduction plate 121.

FIG. 5B shows the inside of the reflection type volume hologramdiffraction grating 122 in an enlarged scale. Referring to FIG. 5B, thereflection type volume hologram diffraction grating 122 is disposed on aface 121A of the first light conduction plate 121 which opposes to thesecond light conduction plate 131 or 331. Thus, part of light incidentto the first light conduction plate 121 is diffracted by the reflectiontype volume hologram diffraction grating 122 and is totally reflectedonce in the inside the first light conduction plate 121. Then, the lightis totally reflected by the surface 122A of the reflection type volumehologram diffraction grating 122 and diffracted by the reflection typevolume hologram diffraction grating 122, whereafter it is emitted fromthe first light conduction plate 121. Meanwhile, the remaining part ofthe light incident to the first light conduction plate 121 passesthrough and is emitted from the first light conduction plate 121 and thereflection type volume hologram diffraction grating 122. In particular,in the embodiments 1 to 4, “emission of light from the first lightconduction section by two times of total reflection” is adopted. Then,in order to make the light amount of the part and the light amount ofthe remaining part of the light in the first light conduction plate 121equal to each other to establish uniformity of the intensitydistribution of the light to be emitted from the entire first lightconduction section 120, where the reflection efficiency of thereflection type volume hologram diffraction grating 122 is representedby η and the light transmission factor T is T=1, the reflectionefficiency η is set to 0.62.

Further, by adopting such a configuration as described above, it ispossible to make the beam diameter along the Z direction of light to beemitted from the first light conduction plate 121 greater by twice thanthe beam diameter along the Z direction of light to be incident to thefirst light conduction plate 121. In other words, the first lightconduction section 120 functions as a kind of expander. Accordingly, theshape of a light flux emitted from the image production apparatus 110 toenter the first light conduction section 120 is deformed appropriatelyby the first light conduction section 120, and the light flux of thedeformed shape enters the second light conduction section 130 or 330.Therefore, there is no necessity to set the diameter of the aperturestop in the Z direction in the image formation apparatus 111 to a greatdiameter. In other words, there is no necessity to increase the diameterof the lens provided in the collimate optical system 112 provided in theimage formation apparatus 111, and reduction in size and weight of theimage displaying apparatus can be anticipated. Further, such a problemthat the display contrast drops and the picture quality is deteriorateddoes not occur.

If the surface 122A of the reflection type volume hologram diffractiongrating 122 is not sufficiently smooth or flat, then the light may bescattered or drop of the contrast or deterioration of the resolution mayoccur. From a point of view of prevention of occurrence of such aproblem as just described and also of protection of the reflection typevolume hologram diffraction grating 122, the first light conductionsection 120 may otherwise be configured such that the first lightconduction plate 121, reflection type volume hologram diffractiongrating 122 and transparent parallel flat plat are laminated in orderfrom the light incidence side. This also applies similarly to the otherembodiments described below.

Embodiment 2

The embodiment 2 is a modification to the embodiment 1 and relates tothe image production apparatus 210 of the second mode. The imagedisplaying apparatus 200 of the embodiment 2 or an image displayingapparatus 400 of the embodiment 4 hereinafter described includes, asshown in FIG. 2 or 4,

(A-1) a light source 261;

(A-2) a collimate optical system 262 for converting light emitted fromthe light source 261 into parallel light;

(A-3) a scanning section 263 for scanning the parallel light emittedfrom the collimate optical system 262; and

(A-4) a relay optical system 264 for relaying the parallel light scannedby the scanning section 263; and

a light flux of the parallel light obtained by the conversion by therelay optical system 264 is introduced to the first light conductionsection 120.

The first light conduction section 120 and the second light conductionsection 130 have a configuration and a structure similar to those of thefirst light conduction section 120 and the second light conductionsection 130 described hereinabove in connection with the embodiment 1,respectively, and therefore, overlapping description of them is omittedherein to avoid redundancy.

A light source 261 includes a red light emitting element 261R foremitting red light, a green light emitting element 261G for emittinggreen light and a blue light emitting element 261B for emitting bluelight, each formed from a semiconductor laser element. Light of thethree primary colors emitted from the light source 261 passes through across prism 265, whereupon color synthesis is carried out to form asingle light flux. The resulting light enters a collimate optical system262 which generally has a positive optical power and emerges as parallellight from the collimate optical system 262. The parallel light isreflected by a total reflection mirror 266 and then subjected tohorizontal scanning and vertical scanning by a scanning section 263formed from an MEMS which includes micromirrors disposed for rotation intwo-dimensional directions and can scan the incoming parallel lighttwo-dimensionally so that the parallel light is converted into a kind ofa two-dimensional image and virtual pixels are produced. Then, lightfrom the virtual pixels passes through a relay optical system 264 formedfrom a well-known relay optical system, and a light flux in the form ofparallel light enters the first light conduction section 120 and thesecond light conduction section 130.

Embodiment 3

Also the embodiment 3 is a modification to the embodiment 1. Referringto FIG. 3A, the image formation apparatus 111 and collimate opticalsystem 112 and the first light conduction section 120 in the imagedisplaying apparatus 300 of the embodiment 3 have a configuration and astructure same as those of the image formation apparatus 111 andcollimate optical system 112 and the first light conduction section 120described hereinabove in connection with the embodiment 1, respectively.Although the second light conduction section 330 is different in theconfiguration and structure of the first and second deflection sections,also it has a basic configuration and structure similar to those of thesecond light conduction section 130 in the embodiment 1. In particular,the second light conduction section 330 includes

(C-1) a second light conduction plate 331 adapted to propagate incominglight in the inside thereof by total reflection and then emit the light;

(C-2) a first deflection section 340 disposed on the second lightconduction plate 331 and adapted to deflect light incident to the secondlight conduction plate 331 such that the light introduced to the secondlight conduction plate 331 is totally reflected in the inside of thesecond light conduction plate 331; and

(C-3) a second deflection section 350 disposed on the second lightconduction plate 331 and adapted to deflect the light propagated in theinside of the second light conduction plate 331 by total reflection overa plural number of times in order to emit the light propagated in theinside of the second light conduction plate 331 by total reflection fromthe second light conduction plate 331.

In the embodiment 3, the first and second deflection sections aredisposed on the surface of the second light conduction plate 331,particularly on the second face 333 of the second light conduction plate331. The first deflection section diffracts light entering the secondlight conduction plate 331, and the second deflection section diffractslight, which has propagated in the inside of the second light conductionplate 331, by total reflection, over a plural number of times. Each ofthe first and second deflection sections is formed from a diffractiongrating element, particularly a reflection type diffraction gratingelement, more particularly a reflection type volume hologram diffractiongrating. In the following description, the first deflection sectionformed from a reflection type volume hologram diffraction grating isreferred to as “first diffraction grating member 340” for theconvenience of description, and the second deflection section formedfrom a reflection type volume hologram diffraction grating is referredto as “second diffraction grating member 350” for the convenience ofdescription.

In the embodiment 3 or the embodiment 4 hereinafter described, in orderto make the first diffraction grating member 340 and the seconddiffraction grating member 350 ready for diffraction reflection of P(here P=3 for red, green and blue) different kinds of light having Pdifferent wavelength bands or wavelengths, the first diffraction gratingmember 340 and the second diffraction grating member 350 are formed bylaminating P diffraction grating layers each formed from a reflectiontype volume hologram diffraction grating. It is to be noted that, ineach diffraction grating layer made of a photopolymer material,interference fringes corresponding to one frequency band or frequencyare formed, and the diffraction grating layers are produced by ahitherto known method. More particularly, the first diffraction gratingmember 340 and the second diffraction grating member 350 have astructure wherein a diffraction grating layer for diffracting andreflecting red light, another diffraction grating layer for diffractingand reflecting green light and a further diffraction grating layer fordiffracting and reflecting blue light are laminated. The pitch of theinterference fringes formed on the diffraction grating layers ordiffraction optical elements is fixed, and the interference fringes havea linear form and extend in parallel to the Z direction. It is to benoted that, in FIGS. 3A and 4, the first diffraction grating member 340and the second diffraction grating member 350 are shown with a singlelayer. Adoption of such a configuration as just described can achieveincrease of the diffraction efficiency, increase of the diffractionreception angle and optimization of the diffraction angle when lighthaving the frequency bands or frequencies is diffracted and reflected bythe first diffraction grating member 340 and the second diffractiongrating member 350.

FIG. 3B shows an enlarged schematic partial section of a reflection typevolume hologram diffraction grating. Referring to FIG. 3B, thereflection type volume hologram diffraction grating has interferencefringes having an inclination angle φ formed therein. Here, theinclination angle φ is defined by the surface and the interferencefringes of the reflection type volume hologram diffraction grating. Theinterference fringes are formed from the inside to the surface of thereflection type volume hologram diffraction grating. The interferencefringes satisfy the Bragg condition. The Bragg condition is a conditionwhich satisfies the following expression (A):

m·λ=2·d·sin(θ)  (A)

where m is a positive integer, λ a wavelength, d the pitch of thegrating face, that is, the distance in a normal direction of a virtualplane including the interference fringes, and θ the complementary angleto the angle at which light enters the interference fringes. Meanwhile,the relationship between the inclination angle φ and the incidence angleψ where light enters the diffraction grating member at the incidenceangle ψ is given by the following expression (B):

θ=90°−(φ+ψ)  (B)

The first diffraction grating member 340 is disposed on, that is,adhered to, the second face 333 of the second light conduction plate 331as described hereinabove, and diffracts and reflects parallel lightentering the second light conduction plate 331 from the first face 332so as to be totally reflected in the inside of the second lightconduction plate 331. Further, the second diffraction grating member 350is disposed on or adhered to the second face 333 of the second lightconduction plate 331 as described hereinabove, and diffracts andreflects the parallel light, which has propagated in the inside of thesecond light conduction plate 331 by total reflection, by a pluralnumber of times such that the light is emitted from the first face 332of the second light conduction plate 331 while it remains in the form ofparallel light. However, the configuration of the incident and emergentfaces is not limited to this, but the second light conduction plateincidence face may be formed from the second face 333 and the secondlight conduction plate emergence face may be formed from the first face332.

Also the second light conduction plate 331 is configured such thatparallel light of the three colors of red, green and blue propagates inthe inside thereof by total reflection and then emerges therefrom. Atthis time, since the second light conduction plate 331 is thin and thelight path of light advancing in the inside of the second lightconduction plate 331 is long, the number of times of total reflection tothe second diffraction grating member 350 differs depending upon theangle of view, that is, the horizontal angle of view. More particularly,the number of times of reflection of parallel light entering with anangle, that is, a horizontal angle of view, of a direction in which itapproaches the second diffraction grating member 350 from withinparallel light which enters the second light conduction plate 331 issmaller than the number of times of reflection of parallel light whichenters the second light conduction plate 331 with a horizontal angle ofview of a direction in which it is spaced away from the seconddiffraction grating member 350. This is because the angle which isdefined by the parallel light diffracted and reflected by the firstdiffraction grating member 340 and entering the second light conductionplate 331 with a horizontal angle of view of a direction in which itapproaches the second diffraction grating member 350 and a normal to thesecond light conduction plate 331 when light propagating in the insideof the second light conduction plate 331 collides with the inner face ofthe second light conduction plate 331 is smaller than the angle which isdefined by the parallel light entering the second light conduction plate331 with a horizontal angle of view of the opposite direction and thenormal to the second light conduction plate 331. Further, the shape ofthe interference fringes formed in the inside of the second diffractiongrating member 350 and the shape of the interference fringes formed inthe inside of the first diffraction grating member 340 have asymmetrical relationship to each other with respect to the XZ plane ofthe second light conduction plate 331.

Also the second light conduction plate 331 in the embodiment 4 describedsubsequently has a configuration and a structure basically same as thoseof the second light conduction plate 331 described above.

In the embodiment 3, where the light propagation direction by internaltotal reflection in the second light conduction plate 331 is defined asY direction and the thicknesswise direction of the second lightconduction plate 331 is defined as X direction, the direction in whichthe interference fringes in the first diffraction grating member 340 andthe second diffraction grating member 350 are juxtaposed, that is, thediffraction direction, is the Y direction. Further, the direction inwhich the interference fringes in the reflection type volume hologramdiffraction grating 122 which forms the first light conduction section120, that is, the diffraction grating of the reflection type volumehologram diffraction grating 122, is the Z direction.

In the embodiment 3, the distance between the centers of the firstdeflection section, that is, the first diffraction grating member 340,and the second defection section, that is, the second diffractiongrating member 350, is 30 mm, and the wavelength of the incident lightis 522 nm. Further, the diffraction angle of incident light entering at0 degree into the second light conduction plate 331, that is, the totalreflection angle in the second light conduction plate 331, is 59degrees. Further, the thickness of the second light conduction plate 331is 1.5 mm and the refractive index is 1.52 while the eye relief is 15mm. At this time, the distance from an incident point to the secondlight conduction plate 331 of light which collides with the center ofthe first diffraction grating member 340 (such incident point ishereinafter referred to as “light incident point”) to the pupil of theobserver is 40 mm in the air conversion length. Then, when thehorizontal angle of view is in the negative, the distance from the lightincident point to the pupil 41 of the observer is greatest. Here, if thehorizontal angle of view is ±11 degrees and the vertical angle of viewis ±8.3 degrees, then the air conversion length of the distance from thelight incident point of a ray of light having a horizontal angle of viewof −11 degrees to the pupil 41 of the observer is 47 mm. It is necessaryto assure an aperture stop (clear aperture) of the vertical angle ofview of ±8.3 degrees at the distance of 48 mm. Accordingly, the apertureof the projection optical system necessary in the vertical direction is,where the diameter of the pupil of the observer is 3 mm, 17 mm. Thisaperture corresponds to the length of the light emerging region of thefirst light conduction section 120 along the Z direction. Where thethickness of the first light conduction plate 121 is 3 mm, therefractive index is 1.52, the wavelength of incidence light is 522 nmand the diffraction angle of 0-degree incidence light, that is, thetotal reflection angle in the first light conduction plate 121, is 59degrees, the diffractive angle corresponding to the angle of view of−8.3 degrees is 49.7 degrees, and the distance over which the lightadvances by one time of total reflection (refer to “L” in FIG. 5B) is7.1 mm. Through such a procedure of calculation as described above, theaperture of the lens provided in the image formation apparatus which isnecessary to introduce parallel light into the first light conductionsection 120 is determined to be 10.5 mm.

As described above, in the embodiment 3, where the light propagationdirection by internal total reflection in the second light conductionplate 331 is defined as Y direction and the thicknesswise direction ofthe second light conduction plate 331 is defined as X direction, thediffraction direction by the first diffraction grating member 340 andthe second diffraction grating member 350 is the Y direction and thediffraction direction by the reflection type volume hologram diffractiongrating 122 which forms the first light conduction section 120 is the Zdirection. In this instance, a phase difference plate for varying thephase difference of a polarized light component emitted from the firstlight conduction plate 121 may be disposed between the first lightconduction plate 121 and the second light conduction plate 331. It is tobe noted that preferably the polarized light component emitted from thefirst light conduction plate 121 is made parallel to the Z direction. Inother words, the phase difference plate may be disposed such that thepolarized light component to enter the first diffraction grating member340 may be parallel to the Z direction. Here, the phase difference platemay be a half-wave plate or two quarter-wave plates, and an S polarizedlight component should be introduced into the first diffraction gratingmember 340. Further, a second phase difference plate for varying thephase difference of a polarized light component emitted from thecollimate optical system or the relay optical system may be disposedbetween the collimate optical system or the relay optical system and thefirst light conduction plate 121. In this instance, preferably thesecond phase plate is disposed such that the polarized light componentto enter the first light conduction plate 121 becomes parallel to the Ydirection. Here, the phase difference plate may be a half-wave plate ortwo quarter-wave plates, and an S polarized light component should beintroduced into the reflection type volume hologram diffraction grating122. This similarly applies also to the embodiment 4 described below,and a second phase difference plate may be disposed also in theembodiment 1 or the embodiment 2. Although preferably a polarized lightcomponent of light passing through the phase difference plate isparallel to the Z direction as described above, the reason is such asdescribed below. In particular, an incident light ray is reflected andBragg diffracted by the interference fringes, and the diffracted lightemerges (refer to FIG. 3B which is an enlarged schematic partialsectional view of a reflection type volume hologram diffractiongrating). Here, the “polarized light component which is parallel to theplane of the figure and perpendicular to the incident light” isconsidered to enter as “p polarized light” into the interferencefringes. On the other hand, the “polarized light component perpendicularto the plane of the figure” is considered to enter as “s polarizedlight” to the interference fringes. The diffraction efficiency of thereflection type volume hologram diffraction grating has a polarizationdependency, and the diffraction efficiency of “p polarized light” islower than that of “s polarized light.” Accordingly, from a point ofview of raising the light utilization efficiency, preferably thepolarized light to be introduced into the reflection type volumehologram diffraction grating is “s polarized light.”

Embodiment 4

The embodiment 4 is a modification to the embodiment 3. The imagedisplaying apparatus of the embodiment 4 is conceptually shown in FIG.4. The light source 261, collimate optical system 262, scanning section263, relay optical system 264 and so forth of the image displayingapparatus of the embodiment 4 have a configuration and a structure sameas those of the embodiment 2. Further, the second light conductionsection 330 in the embodiment 4 has a configuration and a structure sameas those of the second light conduction section 330 in the embodiment 3.

Embodiment 5

The embodiment 5 relates to the image displaying apparatus according tothe first mode of the present invention, and more particularly to ahead-mounted type display unit in which any one of the image displayingapparatus 100, 200, 300 and 400 described hereinabove in connection withthe embodiments 1 to 4, respectively. A schematic view of thehead-mounted type display unit of the embodiment 5 as viewed from thefront is shown in FIG. 6, and a schematic view of the head-mounted typedisplay unit of the embodiment 5 as viewed from the front where a frameis removed is shown in FIG. 7. Further, a schematic view of thehead-mounted type display unit of the embodiment as viewed from above isshown in FIG. 8, and a view of the head-mounted type display unit of theembodiment 5 in a state wherein it is mounted on the head of an observer40 as viewed from above is shown in FIG. 9. It is to be noted that FIG.9 only shows the image displaying apparatus for the convenience ofdescription while the frame is omitted. Further, while, in the followingdescription, the image display apparatus described is represented by theimage displaying apparatus 100, it is a matter of course that it ispossible to apply the image displaying apparatus 200, 300 and 400.

The head-mounted type display unit of the embodiment 5 includes:

(A) a frame 10 of the glasses type adapted to be mounted on the head ofan observer 40; and

(B) two image display apparatus 100. It is to be noted that thehead-mounted type display unit in the present embodiment 5 or theembodiment 6 hereinafter described is of the both-eye type including twoimage display apparatus 100.

The head-mounted type display unit of the embodiment 5 further includesa coupling member 20 for coupling the two image display apparatus 100.The coupling member 20 is attached to the side, which opposes to theobserver, of a central portion 10C of a frame 10 positioned between thetwo pupils 41 of the observer 40, that is, to a location between theobserver 40 and the frame 10, for example, using a screw not shown.Further, a projection image of the coupling member 20 is included in aprojection image of the frame 10. In particular, when the head-mountedtype display unit is viewed from the front of the observer 40, thecoupling member 20 is hidden by the frame 10 and cannot be visuallyobserved. Further, while the two image display apparatus 100 areconnected to each other by the coupling member 20, particularly imagereproduction apparatus 110A and 110B are attached to the opposite endportions of the coupling member 20 such that the attached state thereofcan be adjusted. The image reproduction apparatus 110A and 110B arepositioned on the outer side with respect to the pupils 41 of theobserver 40. In particular, where the distance between the attachedportion center 110A_(c) of the image production apparatus 110A and anend portion 10A of the frame 10 is represented by α, the distance fromthe center 20 _(c) of the coupling member 20 to the end portion 10A ofthe frame 10 by β, the distance between the attached portion center110B_(c) of the other image production apparatus 110B and the endportion 10A of the frame 10 by γ, and the length of the frame 10 b L,the following expressions are satisfied:

α=0.1×L

β=0.5×L

γ=0.9×L

Attachment of the image production apparatus, particularly the imagereproduction apparatus 110A and 110B, to the opposite end portions ofthe coupling member 20 is carried out in the following manner. Inparticular, for example, through holes (not shown) are provided in threeportions at each end of the coupling member, a tapped hole correspondingto a through-hole, that is, a threaded portion not shown, is provided inthe image reproduction apparatus 110A and 110B, and a screw not shown isinserted into each of the through-holes and screwed into the tapped holeprovided in each of the image reproduction apparatus 110A and 110B. Aspring is inserted between the screw and the tapped hole in advance.Thus, the attachment state of each image production apparatus, that is,the inclination of each image production apparatus with respect to thecoupling member, can be adjusted by the tightened state of the screw.After the attachment, the screws are hidden by lids not shown. It is tobe noted that, in FIGS. 7 and 11, slanting lines are applied to thecoupling members 20 and 30 in order to clearly indicate the couplingmembers 20 and 30, respectively.

The frame 10 includes a front portion 10B disposed in front of theobserver 40, two temple portions 12 pivotally attached to the oppositeends of the front portion 10B through hinges 11, and two modern portions(also called end cells or ear pads) attached to end portions of thetemple portions 12. The coupling member 20 is attached to the centralportion 100 of the front portion 10B positioned between the two pupils41 of the observer 40. The central portion 10C corresponds to a bridgein ordinary glasses. Nose pads 14 are attached to, the side of thecoupling member 20 opposing to the observer 40. It is to be noted that,in FIGS. 8 and 12, the nose pads 14 are omitted. The frame 10 and thecoupling member 20 are made of a metal or plastic material, and thecoupling member 20 has shape of a curved bar.

Further, a wiring line 15 including a signal line and a power supplyline and extending from the image production apparatus 110A extends froman end portion of the corresponding modern section 13 to the outsidethrough the inside of the corresponding temple section 12 and the modernsection 13. Further, the image reproduction apparatus 110A and 110B havea headphone section 16, and a headphone section wiring line 17 extendingfrom each of the image reproduction apparatus 110A and 110B extends froman end portion of the corresponding modern section 13 to thecorresponding headphone section 16 through the inside temple section 12and the inside of the modern section 13. More particularly, theheadphone section wiring line 17 extends from an end portion of themodern section 13 to the headphone section 16 such that it goes roundthe rear side of the auricle. By such a configuration as just described,the head-mounted type display unit does not give such an impression thatthe headphone sections 16 and the headphone section wiring lines 17 aredisposed disorderly to the observer but gives a fine feeling.

To the central portion 10C of the front portion 10B, an image pickupapparatus 18 is attached which includes a solid-state image pickupelement formed from CCD (Charge coupled device) or CMOS (Complementarymetal oxide semiconductor) sensors and a lens all not shown. Inparticular, a through-hole is formed at the central portion 10C of theframe 10, and a recessed portion is provided at a portion of thecoupling member 20 opposing to the through-hole provided at the centralportion 10C. The image pickup apparatus 18 is disposed in the recessedportion. Light entering through the through-hole provided in the centralportion 10C is focused on the solid-state image pickup element by thelens. A signal from the solid-state image pickup element is sent to theimage production apparatus 110A through a wiring line not shownextending from the image pickup apparatus 18 and further to an externalcircuit. It is to be noted that the wiring line passes between thecoupling member 20 and the front portion 10B and is connected to theimage production apparatus 110A. By the configuration described, theuser is less likely to visually confirm that the image pickup apparatus18 is incorporated in the head-mounted type display unit.

In this manner, in the head-mounted type display unit (HMD) of theembodiment 5, the coupling member 20 couples the two image displayapparatus 100 to each other, and this coupling member 20 is attached tothe central portion 100 of the frame 10 positioned between the twopupils 41 of the observer 40. In particular, each of the image displayapparatus 100 is not structured such that it is attached directly to theframe 10. Accordingly, when the observer 40 mounts the frame 10 on thehead thereof, the temple portions 12 are placed into an outwardlyexpanded state, and as a result, even if the frame 10 is deformed, nodisplacement or positional variation of the image reproduction apparatus110A and 110B occurs, and even if such displacement occurs, the amountthereof is very small. Therefore, the convergence angle of the left andright images can be prevented from varying with certainty. Besides,since there is no necessity to raise the rigidity of the front portion10B of the frame 10, increase in weight of the frame 10, degradation indesign property and increase in cost are not caused. Further, since theimage displaying apparatus 100 is not attached directly to the frame 10of the glasses type, it is possible to freely select the design, colorand so forth of the frame 10 in accordance with the liking of theobserver and the degree of freedom in design is high with therestriction to the design of the frame 10 reduced. In addition, when thehead-mounted type display unit is viewed from the front of the observer,the coupling member 20 is hidden by the frame 10. This can provide ahigh design property to the head-mounted type display unit.

Embodiment 6

The embodiment 6 is a modification to the embodiment 5. A schematic viewof the head-mounted type display unit of the embodiment 6 as viewed fromthe front is shown in FIG. 10, and another schematic view of thehead-mounted type display unit of the embodiment as viewed from thefront where a frame is removed is shown in FIG. 11. A further schematicview of the head-mounted type display unit of the embodiment 6 as viewedfrom above is shown in FIG. 12.

In the head-mounted type display unit of the embodiment 6, a couplingmember 30 in the form of a bar is different from that in the embodiment5 in that it couples two second light conduction sections 130 to eachother in place of coupling the two image reproduction apparatus 110A and110B to each other. It is to be noted that it is possible to produce thetwo second light conduction sections 130 integrally with each other andattach the coupling member 30 to the integrated second light conductionsections 130.

Also in the head-mounted type display unit of the embodiment 6, thecoupling member 30 is attached to the central portion 10C of the frame10 positioned between the two pupils 41 of the observer 40, for example,using a screw, and the image production apparatus 110 are positioned onthe outer sides with respect to the pupils 41. It is to be noted thatthe image production apparatus 110 are attached to the opposite endportions of the second light conduction section 130. Where the distancefrom the center 30 _(c) of the coupling member 30 to one end portion ofthe frame 10 is represented by β and the length of the frame 10 by L,β=0.5×L is satisfied. It is to be noted that, also in the embodiment 6,the value of α′ and the value of γ′ are equal to the values of α and γin the embodiment 5, respectively.

In the embodiment 6, the frame 10 and the image displaying apparatushave a configuration and a structure same as those of the frame 10 andthe image displaying apparatus described hereinabove in connection withthe embodiment 5, respectively. Therefore, detailed description of themis omitted herein to avoid redundancy. Also the head-mounted typedisplay unit of the embodiment 6 has a configuration and a structuresubstantially same as those of the head-mounted type display unit of theembodiment 5 except the differences described above, and therefore,overlapping description of the same is omitted hereinto avoidredundancy.

Embodiment 7

The embodiment 7 relates to an image display apparatus according to thesecond mode of the present invention and an optical apparatus accordingto the second mode of the present invention and further to the imageproduction apparatus according to the first or second form of thepresent invention. The image display apparatus in the embodiment 7 isconceptually shown in FIG. 14 or 15, and an arrangement state of theimage production apparatus, beam expansion section and light conductionsection (referred to as “second light conduction section” from arelationship to the other embodiments) is schematically illustrated inFIG. 13A. It is to be noted that the image displaying apparatus shown inFIG. 14 is configured such that the beam expansion section in theembodiment 7 is applied to the image displaying apparatus of theembodiment 3 shown in FIGS. 3A and 3B. Meanwhile, the image displayingapparatus shown in FIG. 15 is configured such that the beam expansionsection in the embodiment 7 is applied to the image displaying apparatusof the embodiment 4 shown in FIG. 4.

The image displaying apparatus 700 or 800 according the embodiment 7 oran embodiment 8 hereinafter described includes:

(A) an image production apparatus 110 or 210; and

(B) a light conduction section (second light conduction section 130 or330) adapted to receive and conduct light outputted from the imageproduction apparatus 110 or 210 and then emit the light toward the pupil41 of an observer 40. The light conduction section (second lightconduction section 130 or 330) includes:

(B-1) a light conduction plate (second light conduction plate 131 or331) for propagating the incident light by total reflection in theinside thereof and emitting the propagated light therefrom;

(B-2) a first deflection section 140 or 340 disposed on the lightconduction plate (second light conduction plate 131 or 331) and adaptedto deflect the light incident to the light conduction plate (secondlight conduction plate 131 or 331) so that the light incident to thelight conduction plate (second light conduction plate 131 or 331) istotally reflected in the inside of the light conduction plate (secondlight conduction plate 131 or 331); and

(B-3) a second deflection section 150 or 350 disposed on the lightconduction plate (second light conduction plate 131 or 331) and adaptedto deflect the light propagated in the inside of the light conductionplate (second light conduction plate 131 or 331) by total reflectionover a plural number of times in order to emit the light propagated inthe inside of the light conduction plate (second light conduction, plate131 or 331) by total reflection from the light conduction plate (secondlight conduction plate 131 or 331). It is to be noted that the secondlight conduction section 130 or 330 is of the sea-through type orhalf-transmission type.

Meanwhile, the optical apparatus according to the embodiment 7 or theembodiment 8 hereinafter described includes a light conduction section(second light conduction section 130 or 330) adapted to receive, conductand emit a light flux. The light conduction section (second lightconduction section 130 or 330) includes:

a light conduction plate (second light conduction plate 131 or 331) forpropagating the incident light by total reflection in the inside thereofand emitting the propagated light therefrom;

a first deflection section 140 or 340 disposed on the light conductionplate (second light conduction plate 131 or 331) and adapted to deflectthe light incident to the light conduction plate (second lightconduction plate 131 or 331) so that the light incident to the lightconduction plate (second light conduction plate 131 or 331) is totallyreflected in the inside of the light conduction plate (second lightconduction plate 131 or 331); and

a second deflection section 150 or 350 disposed on the light conductionplate (second light conduction plate 131 or 331) and adapted to deflectthe light propagated in the inside of the light conduction plate (secondlight conduction plate 131 or 331) by total reflection over a pluralnumber of times in order to emit the light propagated in the inside ofthe light conduction plate (second light conduction plate 131 or 331) bytotal reflection from the light conduction plate (second lightconduction plate 131 or 331).

Further, in the embodiment 7 or the embodiment 8 hereinafter described,the image displaying apparatus or the optical apparatus further includesa beam expansion section 710 or 810 adapted to expand, where an enteringdirection of the light flux into the light conduction plate (secondlight conduction plate 131 or 331) and a propagation direction of thelight in the light conduction plate (second light conduction plate 131or 331) are defined as an X direction (in the drawings, indicated by a−X direction) and a Y direction, respectively, the light along a Zdirection different from the X and Y directions and emit the expandedlight to the light conduction section.

In the embodiment 7, as shown in FIG. 13A, the beam expansion section710 includes a first reflecting mirror 711 and a second reflectingmirror 712. The first reflecting mirror 711 is positioned on theopposite side to the image production apparatus with respect to thelight conduction section, that is, with respect to the second lightconduction section 330, that is, positioned on the opposite side to thelight entering side of the light conduction section, while the secondreflecting mirror 712 is positioned adjacent the image productionapparatus with respect to the light conduction section, that is,positioned on the light entering side of the light conduction section.Then, part of the light emitted from the image production apparatuspasses through the light conduction plate and first deflection section,that is, the second light conduction section 330. Thereafter, a seriesof operations that the light passing through the second light conductionsection 330 is reflected by the first reflecting mirror 711 and passesthrough the light conduction plate and the first deflection section,that is, the second light conduction section 330, and then is reflectedby the second reflecting mirror 712, whereafter part of the reflectedlight passes through the light conduction plate and the first deflectionsection, that is, the second light conduction section 330, is repeatedby a predetermined number of times. In the example illustrated in FIG.13A, the light is reflected twice by the second reflecting mirror 712.Where the first reflecting mirror 711 and the second reflecting mirror712 extend in parallel to each other and light is reflected twice by thesecond reflecting mirror 712, the light which begins to propagate in theinside of the light conductor plate, that is, the second lightconduction plate 331, is finally elongated by approximate three times inthe Z direction of the light which first enters the light conductionplate, that is, the second light conduction plate 331.

Here, the first reflecting mirror 711 and the second reflecting mirror712 preferably extend in parallel to each other. Further, the lightentering the light conduction plate, that is, the second lightconduction plate 331, may first be incident perpendicularly to the lightconduction plate, that is, to the second light conduction plate 331, ormay enter at a certain incident angle other than 0 degrees.

Meanwhile, where the first diffraction grating member 340 is formed froma reflection type volume hologram diffraction grating, the lighttransmission factor T of the reflection type volume hologram diffractiongrating can be set, for example, to 0.1 to 0.9 by selection of thematerial to be used for the reflection type volume hologram diffractiongrating, optimization of the thickness of the reflection type volumehologram diffraction grating and optimization of the refractive indexmodulation degree. Δn of the reflection type volume hologram diffractiongrating. The light transmission factor T may be determined, for example,by carrying out various tests. Or, the light transmission factor T maybe varied along the Z direction. By the countermeasures, the differencein brightness in the Z direction of the light which propagates in theinside of the light conduction plate, that is, of the second lightconduction plate 331, can be reduced.

Where light which first enters the light conduction plate, that is, thesecond light conduction plate 331, enters perpendicularly into the lightconduction plate, that is, into the second light conduction plate 331,and the first reflecting mirror 711 and the second reflecting mirror 712extend in parallel to each other and besides the distance between thefirst reflecting mirror 711 and the second reflecting mirror 712, thatis, the length of a normal to the first reflecting mirror 711 when thenormal crosses with the second reflecting mirror 712, is represented byL₀, the angle defined by the first reflecting mirror 711 and theconduction plate, that is, the second light conduction plate 331, isrepresented by θ_(d), the incidence angle when the light enters thefirst reflecting mirror 711 is represented by θ_(in) and besides thelength in the Z direction of the light when the light first enters thefirst reflecting mirror 711 is represented by Z₀, L₀, θ_(d), θ_(in) andZ₀ may have a relationship given by the following expression:

Z ₀=2×L ₀×tan(θ_(in))×cos(θ_(d))

By adopting such a configuration as described above, the beam diameterin the Z direction of light to emerge from the beam expansion section710 can be made greater than the beam diameter along the Z direction ofthe light incident to the beam expansion section 710. Accordingly, theshape of the light flux emitted from the image production apparatus toenter the beam expansion section 710 is deformed appropriately by thebeam expansion section 710 and then introduced into the second lightconduction section 330. Therefore, there is no necessity to set a greatdiameter of the aperture stop in the Z direction in the image formationapparatus. In other words, there is no necessity to increase thediameter of the lens provided in the collimate optical system or thelike provided in the image formation apparatus, and reduction in sizeand weight of the image displaying apparatus can be anticipated.Further, such a problem that the display contrast drops and the picturequality deteriorates does not occur. This similarly applies also to theembodiment 8 hereinafter described.

In the image displaying apparatus 700 of the embodiment 7, the imageproduction apparatus 110 includes, similarly as in the embodiment 1:

(A-1) an image formation apparatus 111 having a plurality of pixelsarrayed in a two-dimensional matrix; and

(A-2) a collimate optical system 112 for converting light emitted fromthe pixels of the image formation apparatus 111 into parallel light; and

a light flux of the parallel light obtained by the conversion by thecollimate optical system 112 is introduced to the beam expansion section710.

Alternatively, in the image displaying apparatus 700 of the embodiment7, the image production apparatus 210 includes, similarly as in theembodiment 2:

(A-1) a light source 261;

(A-2) a collimate optical system 262 for converting light emitted fromthe light source 261 into parallel light;

(A-3) a scanning section 263 for scanning the parallel light emittedfrom the collimate optical system 262; and

(A-4) a relay optical system 264 for relaying the parallel light scannedby the scanning section 263; and

a light flux of the parallel light obtained by the conversion by therelay optical system 264 is introduced to the beam expansion section710.

It is to be noted that the light conduction section, that is, the secondlight conduction section 330, may be configured similarly to the secondlight conduction section 330 described hereinabove in connection withthe embodiment 3, and therefore, overlapping description the same isomitted hereinto avoid redundancy. Further, the image displayingapparatus of the embodiment 7 described hereinabove and the imagedisplaying apparatus of the embodiment 8 which is hereinafter describedcan naturally be applied to the head-mounted type display unitsdescribed hereinabove in connection with the embodiments 5 and 6.

Embodiment 8

The embodiment 8 is a modification to the embodiment 7. Image displayapparatus according to the embodiment 8 are conceptually shown in FIGS.16 to 19, and an arrangement state of the image production apparatus,beam expansion section and light conduction section (hereinafterreferred to as “second conduction section” similarly as in thedescription of the embodiment 7) is schematically illustrated in FIG.13B. It is to be noted that the image displaying apparatus shown in FIG.16 is an application of the beam expansion section in the embodiment 8to the image displaying apparatus of the embodiment 3 describedhereinabove with reference to FIG. 3A. Meanwhile, the image displayingapparatus shown in FIG. 17 is an application of the beam expansionsection in the embodiment 8 to the image displaying apparatus of theembodiment 4 described hereinabove with reference to FIG. 4. Further,the image displaying apparatus shown in FIG. 18 is an application of thebeam expansion section in the embodiment 8 to the image displayingapparatus of the embodiment 1 described hereinabove with reference toFIG. 1. Furthermore, the image displaying apparatus shown in FIG. 19 isan application of the beam expansion section in the embodiment 8 to theimage displaying apparatus of the embodiment 2 described hereinabovewith reference to FIG. 2.

In the embodiment 8, the beam expansion section 810 includes ahalf-mirror 811 and a reflecting mirror 812 which are positionedadjacent the image production apparatus with reference to the lightconduction section, that is, on the light incidence side of the lightconduction section. Part of light emitted from the image productionapparatus passes through the half-mirror 811 and enters the lightconduction section, that is, the second light conduction section 130 or330, while the remaining part of the light is reflected by thehalf-mirror 811 and enters the reflecting mirror 812. Then, a series ofoperations that part of the light reflected by the reflecting mirror 812passes through the half-mirror 811 and enters the light conduction, thatis, the second light conduction section 130 or 330 while the remainingpart of the light is reflected by the half-mirror 811 and comes to thereflecting mirror 812 is repeated by a predetermined number of times. Inthe example shown in FIG. 13B, the light is reflected twice by thereflecting mirror 812. Where the half-mirror 811 and the reflectingmirror 812 extend in parallel to each other and light is reflected twiceby the reflecting mirror 812, the light which begins to propagate in theinside of the light conduction plate, that is, of the second lightconduction plate 131 or 331, is finally expanded by approximately threetimes in the Z direction of the light which first enters the lightconduction plate, that is, the second light conduction plate 131 or 331.

Preferably the half-mirror 811 and the reflecting mirror 812 extend inparallel to each other. Further, the light which first enters the lightconduction plate, that is, the second light conduction plate 131 or 331,may be incident perpendicularly to the light conduction plate, that is,to the second light conduction plate 131 or 331 or may be incident at acertain incidence angle other than 0 degrees.

Meanwhile, where the first diffraction section 340 is formed from areflection type volume hologram diffraction grating, the lighttransmission factor T of the reflection type volume hologram diffractiongrating can be set, for example, to 0.1 to 0.9 by selection of thematerial to be used for the reflection type volume hologram diffractiongrating, optimization of the thickness of the reflection type volumehologram diffraction grating and optimization of the refractive indexmodulation degree Δn of the reflection type volume hologram diffractiongrating. The light transmission factor T may be determined, for example,by carrying out various tests. Alternatively, the light transmissionfactor T of the half-mirror 811 may be varied along the Z direction. Bythe countermeasures, the difference in brightness in the Z direction ofthe light which propagates in the inside of the light conduction plate,that is, of the second light conduction plate 331, can be reduced.

Where light which first enters the light conduction plate, that is, thesecond light conduction plate 331, enters perpendicularly into the lightconduction plate, that is, into the second light conduction plate 331,and the half-mirror 811 and the reflecting mirror 812 extend in parallelto each other and besides the distance between the half-mirror 811 andthe reflecting mirror 812, that is, the length of a normal to thehalf-mirror 811 when the normal crosses with the reflecting mirror 812,is represented by L₀, the angle defined by the half-mirror 811 and theconduction plate, that is, the second light conduction plate 331, isrepresented by θ_(d), the incidence angle when the light enters thehalf-mirror 811 is represented by θ_(in) and besides the length in the Zdirection of the light when the light first enters the half-mirror 811is represented by Z₀, a relationship of L₀, θ_(d), θ_(in) and Z₀ mayhave given by the following expression:

Z ₀=2×L ₀×tan(θ_(in))×cos(θ_(d))

It is to be noted that, in the image displaying apparatus 800 of theembodiment 8, the image production apparatus 110 may be configuredsimilarly to that in the embodiment 1 and the image production apparatus210 may be configured similarly to that in the embodiment 2. Further,the light conduction section, that is, the second light conductionsection 130 or 330, may be configured similarly to the second lightconduction section 130 described hereinabove in connection with theembodiment 1 or the second light conduction section 330 describedhereinabove in connection with the embodiment 3. Therefore, detaileddescription of them is omitted herein to avoid redundancy.

Embodiment 9

Also the embodiment 9 is a modification to the embodiment 7. Arrangementstates of the image production apparatus, beam expansion section andlight conduction section in the embodiment 9 as viewed in the Ydirection and the X direction are schematically illustrated in FIGS. 28Aand 28B, respectively. It is to be noted that the second conductionplate 331 is not shown in FIG. 28B, and the second conduction plate 331is not shown in FIG. 30B.

In the beam expansion section 710 described hereinabove in thedescription of the embodiment 7, light which begins to propagate in theinside of the light conduction plate, that is, the second lightconduction plate 331, is finally expanded, for example, to approximatelythree times in the Z direction of the light incident first to the lightconduction plate, that is, to the second light conduction plate 331.However, according to circumstances, there is the possibility that itmay become necessary to set the diameter of the aperture stop in the Ydirection of the image formation apparatus to a great diameter. A lightflux is supposed whose horizontal angle of view assumes a negativemaximum value in the collimate optical system 112 or the relay opticalsystem 264. A behavior of the light flux in the beam expansion section710 when the light flux enters the beam expansion section 710 isschematically illustrated in FIGS. 30A and 30B. Here, FIGS. 30A and 30Billustrate the arrangement states of the image production apparatus,beam expansion section and light conductor section in the embodiment 7as viewed in the Y direction and the Z direction, respectively.

As seen from FIGS. 30A and 30B, a light flux which is repetitivelyreflected between the first reflecting mirror 711 and the secondreflecting mirror 712 gradually moves in the −Y direction. For example,in FIGS. 30A and 30B, a light flux denoted by reference character awhose horizontal angle of view assumes a negative maximum angle collideswith and is reflected by the first reflecting mirror 711 at a point “b”and then collides with and is reflected by the second reflecting mirror712 at another point “c.” Thereafter, the light flux collides with andis reflected by the first reflecting mirror 711 at a further point “d,”and then collides with and is reflected by the second reflecting mirror712 at a still further point “e,” whereafter it enters and is diffractedand reflected by an end portion “f” in the Y direction of the secondlight conduction section 330. In this instance, the light flux enteringthe end portion “f” in the Y direction of the second light conductionsection 330 is displaced by ΔY′ in the −Y direction with reference tothe emerging position “a” from the collimate optical system 112 or therelay optical system 264. Similarly, when another light flux whosehorizontal angle of view assumes a positive maximum value is supposed,the light flux is displaced by ΔY′ in the +Y direction with reference tothe emerging position from the collimate optical system 112 or the relayoptical system 264.

Here, the position of the first deflection section 340 which diffractsand reflects a parallel light flux group emerging from the collimateoptical system 112 or the relay optical system 264 and incoming to thesecond light conduction section 330 becomes the aperture stop positionin the Y direction. Accordingly, it sometimes becomes necessary to setthe diameter in the Y direction of the collimate optical system 112 orthe relay optical system 264 to a great diameter. In particular, in theexample shown in FIGS. 30A and 30B, the diameter in the Y direction ofthe collimate optical system 112 or the relay optical system 264 musthave a value equal to the sum of the length in the Y direction of thefirst deflection section 340 and 2×ΔY′.

In the working example 9, as seen in FIGS. 29A and 29B which show thebeam expansion section in an enlarged scale, the light reflecting facesof a first reflecting mirror 721 and a second reflecting mirror 722which configure a beam expansion section 720 have a plurality of concaveand convex portions 723 and 724, respectively. Here, the concave andconvex portions 723 and 724 extend in planes parallel to a plane definedby the X axis and the Z axis and have a shape of a combination ofadjacent sides to the right angle of a right-angled triangle along the Ydirection when it is assumed to cut the concave and convex portions 723and 724 in planes defined by normal lines to the first reflecting mirror2721 and the second reflecting mirror 2722 and the Y axis. Inparticular, each of the concave and convex portions 723 and 724 has ashape of a rectangular prism whose axial line extends in parallel to aplane defined by the X axis and the Z axis and whose vertical angle is90 degrees. While, in the working example 9, the right-angled triangleis an isosceles triangle having adjacent sides which are equal in lengthto each other and the adjacent sides of the right-angled triangles ofthe same shape along the Y direction are juxtaposed with each other, theconfiguration of the concave and convex portions 723 and 724 is notlimited to this. It is to be noted that a point at which a center lightflux emerging from the center of the collimate optical system 112 or therelay optical system 264 and passing through an image formationapparatus side nodal point enters the first reflecting mirror 721 isdefined as a reflecting mirror central point. Further, an axial linewhich passes the center of the first reflecting mirror and extends inparallel to the X direction is defined as an X axis while another axialline which passes the first reflecting mirror central point and extendsin parallel to the Y direction is defined as a Y axis and a further axisparallel to the Z direction is defined as a Z axis.

Two inclined faces of a light reflecting face corresponding to adjacentsides to the right angle of a write-angled triangle are individuallyreferred to as a first inclined face 723A or 724A and a second inclinedface 723B or 724B for the convenience of description. As seen from FIG.29C which shows an enlarged schematic partial sectional view, lightincident to the first reflecting mirror 721 collides, for example, withthe first inclined face 723A and is reflected by the first inclined face723A, and then collides with and is reflected by the second inclinedface 723B, whereafter it is emitted from the first reflecting mirror721. The light incident to the first inclined face 723A and the lightemerging from the second inclined face 723B are parallel to each other.Similarly, light incident to the second reflecting mirror 722 collides,for example, with and is reflected by the first inclined face 724A andthen collides with and is reflected by the second inclined face 724B,whereafter it is emitted from the second reflecting mirror 722. Thelight incident to the first inclined face 724A and the light emergingfrom the second inclined face 724B are parallel to each other. It is tobe noted that light reflecting layers 725 and 726 made of a lightreflecting material such as, for example, aluminum are provided on thelight reflecting faces of the first reflecting mirror 721 and the secondreflecting mirror 722, respectively.

A light flux whose horizontal angle of view assumes a maximum value inthe collimate optical system 112 or the relay optical system 264 issupposed. A behavior of the beam expansion section 720 when such a lightflux as just described enters the beam expansion section 2720 isschematically illustrated in FIGS. 28A and 28B.

As seen from FIGS. 28A and 28B, reflection of light is repeated betweenthe first reflecting mirror 721 and the second reflecting mirror 722.However, a colliding point of a light flux with the first reflectingmirror 721 and a colliding point of the light flux with the secondreflecting mirror 722 do not move in the Y direction but merely move inthe X direction and the Y direction in principle. For example, in theexample illustrates in FIGS. 28A and 28B, a light flux denoted by “a”whose horizontal angle of view assumes a negative maximum value collideswith and is reflected by the first reflecting mirror 721 at a point “b,”and then collides with and is reflected by the second reflecting mirror722 at another point “c.” Thereafter, the light flux collides with andis reflected by the first reflecting mirror 721 at a further point “d,”and then collides with and is reflected by the second reflecting mirror722 at a still further point “e,” and then enters and is diffracted andreflected by a Y direction end portion “f” of the second lightconduction section 330. In this instance, the light flux entering the Ydirection end portion “f” of the second light conduction section 330 isdisplaced by ΔY in the −Y direction with reference to the emergingposition “a” from the collimate optical system 2112 or the relay opticalsystem 264. Similarly, when another light flux whose horizontal angle ofview assumes a positive maximum value is assumed, the light fluxincident to the Y direction end portion “f” is displaced by ΔY in the +Ydirection with reference to the emerging position from the collimateoptical system 112 or the relay optical system 264. However, the valueof the displacement amount ΔY is lower than the value of thedisplacement amount ΔY′ shown in FIG. 30B.

Here, as described hereinabove, the position of the first deflectionsection 340 which diffracts and reflects a parallel light flux groupemerging from the collimate optical system 112 or the relay opticalsystem 264 and incoming to the second light conduction section 330becomes the aperture stop position in the Y direction. In particular, inthe example shown in FIGS. 28A and 28B, the diameter in the Y directionof the collimate optical system 112 and the relay optical system 264must be set to a value equal to the sum of the length in the Y directionof the first deflection section 340 and 2×ΔY. However, the value of thedisplacement amount ΔY is lower than the value of the displacementamount ΔY′ described hereinabove with reference to FIG. 30B withcertainty. Therefore, there is no necessity to form the first reflectingmirror 2721 and the second reflecting mirror 2722 as reversal mirrors toset the diameter of the collimate optical system 2112 or the relayoptical system 2264 in the Y direction to a great value or, even if thediameter is set to a great value, there is no necessity to make thediameter in the Y direction very much.

Further, in the second light conduction section in the embodiment 3 or4, such a configuration that the first deflection section formed from atransmission type hologram is disposed on the first face 332 of thesecond light conduction plate 331 and a second deflection section formedfrom a reflection type hologram is disposed on the second face 333 maybe adopted.

As a modification to the image forming apparatus suitable for use withthe embodiment 1, 3, 7 or 8, for example, such an image formationapparatus of the active matrix type as conceptually shown in FIG. 20 maybe used. Referring to FIG. 20, the image formation apparatus includes alight emitting panel wherein a plurality of light emitting elements 501each formed from a semiconductor light emitting element are arrayed in atwo-dimensional matrix. The light emitting/no-light emitting state ofeach of the light emitting elements 501 is controlled so that the lightemitting state of the light emitting element 501 is directly visuallyobserved to display an image. Light emitted from the image formationapparatus enters the second light conduction plate 131 or 331 throughthe collimate optical system 112.

Alternatively, the image formation apparatus may be formed as an imageformation apparatus for color display which includes, as conceptuallyshown in FIG. 21,

(α) a red light emitting panel 511R wherein a plurality of red lightemitting elements 501R for emitting red light are arrayed in atwo-dimensional matrix;

(β) a green light emitting panel 511G wherein a plurality of green lightemitting elements 501G for emitting green light are arrayed in atwo-dimensional matrix;

(γ) a blue light emitting panel 511B wherein a plurality of blue lightemitting elements 501B for emitting blue light are arrayed in atwo-dimensional matrix; and

(δ) a member such as, for example, a dichroic prism 503, for integratingthe light emitted from the red light emitting panel 511R, green lightemitting panel 511G and blue light emitting panel 511B into a singlelight flux, and

the light emitting/no-light emitting state of the red light emittingelements 501R, green light emitting element 501G and blue light emittingelements 501B is individually controlled. Also the light emitted fromthis image formation apparatus is introduced to the second lightconduction plate 131 or 331 through the collimate optical system 112. Itis to be noted that reference numeral 512 denotes a microlens elementfor condensing the light emitted from the light emitting elements.

An image formation apparatus including light emitting panels 511R, 511Gand 511B in which such light emitting elements 501R, 501G and 501B asdescribed above are arrayed in a two-dimensional matrix, respectively,is conceptually shown in FIG. 22. Referring to FIG. 22, light emittedfrom the light emitting panels 511R, 511G and 511B is controlled to passor not pass by light passage controlling apparatus 504R, 504G and 504B,respectively, and enters the dichroic prism 503 by which it isintegrated into a single light flux. The light flux is introduced intothe second light conduction plate 131 or 331 through the collimateoptical system 112.

Meanwhile, an image formation apparatus which includes light emittingpanels 511R, 511G and 511B in which the light emitting elements 501R,501G and 501B are arrayed in a two-dimensional matrix, respectively, isshown conceptually shown in FIG. 23. Referring to FIG. 23, light emittedfrom the light emitting panels 511R, 511G and 511B enters the dichroicprism 503, by which fluxes of the light are integrated into a singlelight flux. Then, the light emitted from the dichroic prism 503 iscontrolled to pass or not pass by a light passage controlling apparatus504 and is introduced to the second light conduction plate 131 or 331through the collimate optical system 112.

Alternatively, the image information apparatus may have such aconfiguration as shown in FIG. 24. Referring to FIG. 24, the imageformation apparatus includes a red light emitting element 501R foremitting red light and a light passage controlling apparatus such as,for example, a liquid crystal display apparatus 504R which is a kind oflight valve for controlling passage/non-passage of light emitted fromthe red light emitting element 501R, a green light emitting element 501Gfor emitting green light and a light passage controlling apparatus suchas, for example, a liquid crystal display apparatus 504G which is a kindof light valve for controlling passage/non-passage of light emitted fromthe green light emitting element 501G, and a blue light emitting element501B for emitting blue light and a light passage controlling apparatussuch as, for example, a liquid crystal display apparatus 504B which is akind of light valve for controlling passage/non-passage of light emittedfrom the blue light emitting element 501B. The image formation apparatusfurther includes a light conduction member 502 for conducting lightemitted from each of the light emitting elements 501R, 501G and 501B,which are made of a GaN-based semiconductor, and a member such as, forexample, a dichroic prism 503 for integrating the light conducted by thelight conduction member 502 into a single light flux.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Applications JP 2009-170730 filedin the Japan Patent Office on Jul. 22, 2009, JP 2010-101615 filed in theJapan Patent Office on Apr. 27, 2010 and JP 2010-149346 filed in theJapan Patent Office on Jun. 30, 2010, the entire contents of which ishereby incorporated by reference.

1. An image displaying apparatus, comprising: (A) an image productionapparatus; (B) first light conduction means for receiving, conductingand emitting a light emitted from said image production apparatus; and(C) second light conduction means for receiving and conducting lightemitted from said first light conduction means and then emitting thelight toward the pupil of an observer; said first light conduction meansincluding (B-1) a first light conduction plate for propagating part ofthe incident light by total reflection in the inside thereof andemitting the light therefrom, and (B-2) a reflection type volumehologram diffraction grating disposed on said first light conductionplate, said second light conduction means including (C-1) a second lightconduction plate configured to propagate incoming light in the insidethereof by total reflection and then emit the light, (C-2) firstdeflection means disposed in said second light conduction plate andadapted to deflect light incident to said second light conduction platesuch that the light introduced to said second light conduction plate istotally reflected in the inside of said second light conduction plate,and (C-3) second deflection means disposed in said second lightconduction plate and adapted to deflect the light propagated in theinside of said second light conduction plate by total reflection over aplural number of times in order to emit the light propagated in theinside of said second light conduction plate by total reflection fromsaid second light conduction plate.
 2. The image displaying apparatusaccording to claim 1, wherein said image production apparatus includes:(A-1) an image formation apparatus having a plurality of pixels arrayedin a two-dimensional matrix; and (A-2) a collimate optical system forconverting light emitted from the pixels of said image formationapparatus into parallel light, and a light flux of the parallel lightobtained by the conversion by said collimate optical system isintroduced to said first light conduction means.
 3. The image displayingapparatus according to claim 1, wherein said image production apparatusincludes: (A-1) a light source; (A-2) a collimate optical system forconverting light emitted from said light source into parallel light;(A-3) scanning means for scanning the parallel light emitted from saidcollimate optical system; and (A-4) a relay optical system for relayingthe parallel light scanned by said scanning means, and a light flux ofthe parallel light obtained by the conversion by said relay opticalsystem is introduced to said first light conduction means.
 4. The imagedisplaying apparatus according to claim 1, wherein, where the lightpropagation direction by the total reflection in the inside of saidsecond light conduction plate is represented as Y direction and thethicknesswise direction of said second light conduction plate isrepresented as X direction, the light propagation direction by the totalreflection in the inside of said first light conduction plate is a Zdirection and the thicknesswise direction of said first light conductionplate is the X direction, and the beam diameter along the Z direction ofthe light emitted from said first light conduction plate is greater thanthe beam diameter along the'Z direction of the light incident to saidfirst light conduction plate.
 5. The image displaying apparatusaccording to claim 1, wherein said reflection type volume hologramdiffraction grating is disposed on a face of said first light conductionplate opposing to said second light conduction plate, and part of thelight incident to said first light conduction plate is diffracted bysaid reflection type volume hologram diffraction grating, totallyreflected once in the inside of said first light conduction plate,totally reflected once on the surface of said reflection type volumehologram diffraction grating, diffracted by said reflection type volumehologram diffraction grating and then emitted from said first lightconduction plate while the remaining part of the light incident to saidfirst light conduction plate is emitted from said first light conductionplate after passing through said first light conduction plate and saidreflection type volume hologram diffraction grating.
 6. The imagedisplaying apparatus according to claim 1, wherein said first lightconduction means has a structure wherein said first light conductionplate, said reflection type volume hologram diffraction grating and atransparent parallel flat plate are laminated in order from the lightincidence side.
 7. The image displaying apparatus according to claim 1,wherein said first deflection means is configured from a diffractiongrating element.
 8. The image displaying apparatus according to claim 7,wherein said first deflection means is configured from a reflection typevolume hologram diffraction grating, and where the light propagationdirection by the total reflection in the inside of said second lightconduction plate is represented a Y direction and the thicknesswisedirection of said second light conduction plate is represented as Xdirection, the diffraction direction by said reflection type volumehologram diffraction grating which configures said first deflectionmeans is the Y direction and the diffraction direction by saidreflection type volume hologram diffraction grating which configuressaid first light conduction means is a Z direction.
 9. The imagedisplaying apparatus according to claim 8, further comprising a phasedifference plate disposed between the first light conduction plate andthe second light conduction plate and configured to vary a phasedifference of polarization components outputted from said first lightconduction plate.
 10. The image displaying apparatus according to claim9, wherein the polarization components of the light passing through saidphase difference plate are in parallel to the Z direction.
 11. The imagedisplaying apparatus according to claim 1, wherein said first deflectionmeans diffracts the light incident to said second light conductionplate, and said second deflection means diffracts the light propagatedin the inside of the second light conduction plate by total reflectionover a plural number of times.
 12. The image displaying apparatusaccording to claim 11, wherein said first deflection means and saidsecond deflection means are individually configured from a diffractiongrating element.
 13. The image displaying apparatus according to claim12, wherein said diffraction grating element is configured from areflection type diffraction grating element.
 14. The image displayingapparatus according to claim 12, wherein said diffraction gratingelement is configured from a transmission type diffraction gratingelement.
 15. The image displaying apparatus according to claim 12,wherein one of the diffraction grating elements is configured from areflection type diffraction grating element and the other one of thediffraction grating elements is configured from a transmission typediffraction grating element.
 16. The image displaying apparatusaccording to claim 1, wherein said first deflection means reflects thelight incident to said second light conduction plate; and said seconddeflection means transmits and reflects the light propagated in theinside of said second light conduction plate by total reflection over aplural number of times.
 17. The image displaying apparatus according toclaim 16, wherein said first deflection means functions as a reflectingmirror, and said second deflection means functions as a half-mirror. 18.An optical apparatus, comprising: first light conduction means forreceiving, conducting and emitting a light flux; and second lightconduction means for receiving and conducting the light flux emittedfrom said first light conduction means and then emitting the light, saidfirst light conduction means including (a-1) a first light conductionplate for propagating part of the incident light by total reflection inthe inside thereof and emitting the light therefrom, and (a-2) areflection type volume hologram diffraction grating disposed on saidfirst light conduction plate, said second light conduction meansincluding (b-1) a second light conduction plate configured to propagateincoming light in the inside thereof by total reflection and then emitthe light, (b-2) first deflection means disposed in said second lightconduction plate for deflecting light incident to said second lightconduction plate such that the light introduced to said second lightconduction plate is totally reflected in the inside of said second lightconduction plate, and (b-3) second deflection means disposed in saidsecond light conduction plate for deflecting the light propagated in theinside of said second light conduction plate by total reflection over aplural number of times in order to emit the light propagated in theinside of said second light conduction plate by total reflection fromsaid second light conduction plate.
 19. An image displaying apparatus,comprising: (A) an image production apparatus; and (B) light conductionmeans for receiving and conducting light outputted from said imageproduction apparatus and then emitting the light toward the pupil of anobserver, said light conduction means including (B-1) a light conductionplate for propagating the incident light by total reflection in theinside thereof and emitting the light therefrom, (B-2) first deflectionmeans disposed in said light conduction plate and adapted to deflect thelight incident to said light conduction plate so that the light incidentto said light conduction plate is totally reflected in the inside ofsaid light conduction plate, and (B-3) second deflection means disposedin said light conduction plate and adapted to deflect the lightpropagated in the inside of said light conduction plate by totalreflection over a plural number of times in order to emit the lightpropagated in the inside of said light conduction plate by totalreflection from said light conduction plate, said image displayingapparatus further comprising beam expansion means for expanding, wherean entering direction of the light into said light conduction plate anda propagation direction of the light in said light conduction plate aredefined as an X direction and a Y direction, respectively, the lightemitted from said image production apparatus along a Z direction andemitting the expanded light to said light conduction means.
 20. Theimage displaying apparatus according to claim 19, wherein said beamexpansion means is configured from a first reflecting mirror and asecond reflecting mirror, said first reflecting mirror is positioned onthe opposite side to said image production apparatus with said lightconduction means sandwiched therebetween, and said second reflectingmirror is positioned adjacent said image production apparatus withrespect to said light conduction means.
 21. The image displayingapparatus according to claim 20, wherein part of the light outputtedfrom said image production apparatus repetitively undergoes, in order bya predetermined number of times, passage through said light conductionplate and said first deflection means, reflection by said firstreflecting mirror, passage through said light conduction plate and saidfirst deflection means, reflection by said second reflecting mirror, andpassage of part of the light through said light conduction plate andsaid first deflection means.
 22. The image displaying apparatusaccording to claim 21, wherein each of light reflecting faces of saidfirst and second light conduction plates which configure said beamexpansion section has a plurality of convex and concave portions whichextend in planes parallel to a plane defined by an X axis and a Z axisand have a shape of a combination of adjacent sides to the right angleof a right-angled triangle along the Y direction when it is assumed tocut said concave and convex portions in planes defined by normal linesto said first reflecting mirror and said second reflecting mirror and aY axis.
 23. The image displaying apparatus according to claim 19,wherein said beam expansion means is configured from a half-mirror and areflecting mirror, and said half-mirror and said reflecting mirror arepositioned adjacent said image production apparatus with respect to saidlight conduction means.
 24. The image displaying apparatus according toclaim 23, wherein part of the light emitted from said image productionapparatus passes through said half-mirror and introduced into said lightconduction plate and the remaining part of the light is reflected onsaid half-mirror and introduced into said reflecting mirror, and part ofthe light reflected on said reflecting mirror passes through saidhalf-mirror and introduced into said light conduction plate while theremaining part of the light is reflected on said half-mirror andintroduced into said reflecting mirror, the passage and reflectionactions being repetitively carried out by a predetermined number oftimes.
 25. An optical apparatus, comprising: light conduction means forreceiving, conducting and emitting a light flux, said light conductionmeans including a light conduction plate for propagating the incidentlight by total reflection in the inside thereof and emitting the lighttherefrom, first deflection means disposed in said light conductionplate for deflecting the light incident to said light conduction plateso that the light incident to said light conduction plate is totallyreflected in the inside of said light conduction plate, and seconddeflection means disposed in said light conduction plate for deflectingthe light propagated in the inside of said light conduction plate bytotal reflection over a plural number of times in order to emit thelight propagated in the inside of said light conduction plate by totalreflection from said light conduction plate, said optical apparatusfurther comprising beam expansion means for expanding, where an enteringdirection of the light flux into said light conduction plate and apropagation direction of the light in said light conduction plate aredefined as an X direction and a Y direction, respectively, the lightflux along a Z direction and emitting the expanded light to said lightconduction means.
 26. An image displaying apparatus, comprising: (A) animage production apparatus; (B) first light conduction means forreceiving, conducting and emitting a light emitted from said imageproduction apparatus; and (C) second light conduction means forreceiving and conducting light emitted from said first light conductionmeans and then emitting the light toward the pupil of an observer, saidfirst light conduction means including (B-1) a first light conductionplate for propagating part of the incident light by total reflection inthe inside thereof and emitting the light therefrom, and (B-2) areflection type volume hologram diffraction grating disposed on saidfirst light conduction plate, said second light conduction meansincluding (C-1) a second light conduction plate configured to propagateincoming light in the inside thereof by total reflection and then emitthe light, (C-2) first deflection means disposed in said second lightconduction plate and adapted to deflect light incident to said secondlight conduction plate, and (C-3) second deflection means disposed insaid second light conduction plate and adapted to deflect the lightpropagated in the inside of the second light conduction plate by totalreflection.
 27. The image displaying apparatus according to claim 26,wherein said reflection type volume hologram diffraction grating isdisposed on the face of said first light conduction plate opposing tosaid second light conduction plate.
 28. An image displaying apparatus,comprising: (A) an image production apparatus; and (B) light conductionmeans for receiving and conducting light outputted from said imageproduction apparatus and then emitting the light toward the pupil of anobserver, said light conduction means including (B-1) a light conductionplate for propagating the incident light by total reflection in theinside thereof and emitting the light therefrom, (B-2) first deflectionmeans disposed in said light conduction plate and adapted to deflectlight incident to said light conduction plate, and (B-3) seconddeflection means disposed in said light conduction plate and adapted todeflect the light propagated in the inside of said light conductionplate by total reflection over a plural number of times, said imagedisplaying apparatus further comprising beam expansion means forexpanding, where an entering direction of the light into said lightconduction plate and a propagation direction of the light in said lightconduction plate are defined as a first direction and a seconddirection, respectively, the light emitted from said image productionapparatus along a third direction different from the first direction andthe second direction and emitting the expanded light to said lightconduction means.
 29. The image displaying apparatus according to claim28, wherein said beam expansion means is configured from at least tworeflecting mirrors positioned with said light conduction meanssandwiched therebetween.
 30. An optical apparatus, comprising: a firstlight conduction section configured to receive, conduct and emit a lightflux; and a second light conduction section configured to receive andconduct a light flux emitted from said first light conduction sectionand then emit the light, said first light conduction section including(a-1) a first light conduction plate for propagating part of theincident light by total reflection in the inside thereof and emittingthe light therefrom, and (a-2) a reflection type volume hologramdiffraction grating disposed on said first light conduction plate, saidsecond light conduction section including (b-1) a second lightconduction plate adapted to propagate incoming light in the insidethereof by total reflection and then emit the light, (b-2) a firstdeflection section disposed in said second light conduction plate fordeflecting light incident to said second light conduction plate suchthat the light introduced to said second light conduction plate istotally reflected in the inside of said second light conduction plate,and (b-3) a second deflection section disposed in said second lightconduction plate for deflecting the light propagated in the inside ofsaid second light conduction plate by total reflection over a pluralnumber of times in order to emit the light propagated in the inside ofsaid second light conduction plate by total reflection from said secondlight conduction plate.
 31. An optical apparatus, comprising: a lightconduction section configured to receive, conduct and emit a light flux,said light conduction section including a light conduction plate forpropagating the incident light by total reflection in the inside thereofand emitting the light therefrom, a first deflection section disposed insaid light conduction plate for deflecting the light incident to saidlight conduction plate so that the light incident to said lightconduction plate is totally reflected in the inside of said lightconduction plate, and a second deflection section disposed in said lightconduction plate for deflecting the light propagated in the inside ofsaid light conduction plate by total reflection over a plural number oftimes in order to emit the light propagated in the inside of said lightconduction plate by total reflection from said light conduction plate,said optical apparatus further comprising a beam expansion sectionconfigured to expand, where an entering direction of the light flux intosaid light conduction plate and a propagation direction of the light insaid light conduction plate are defined as an X direction and a Ydirection, respectively, the light flux along a Z direction and emit theexpanded light to said light conduction section.